Bojan Tamburic PhD, is a Chancellor's Postdoctoral Fellow at UTS and Deputy Team Leader of the Algal Biosystems and Biotechnology research group within the Plant Functional Biology and Climate Change Cluster (UTS:C3).
His multidisciplinary research focuses on the efficient cultivation of microalgal biomass. This process may be used to bioremediate wastewater and/or to sequester atmospheric carbon dioxide. The resulting biomass may be used to produce biofuels, aquaculture feed, high-value chemicals such as pigments and antioxidants, or even human food.
Bojan has a background in Applied Physics and Biochemical Engineering. His PhD on the topic of algal hydrogen production was awarded by Imperial College London. Bojan is an international expert on algal bioreactor design, optics and operation.
Bojan is passionate about communicating his research to his colleagues and to the public. His main research outputs include 15 peer-reviewed publications in major scientific journals, 8 speeches at large international conferences (in Australia, UK, USA, Germany, Italy, Portugal and Costa Rica), the invention of a novel bioreactor and its subsequent exhibition at the London Science Museum, an article in The Conversation, and several public lectures and radio interviews.
Can supervise: YES
Application of concepts from the physical sciences and engineering to solve biological challenges, with a particular focus on the field of algal biomass production
Marine Productivity and Climate Change (91156)
Tamburic, B, Evenhuis, CR, Crosswell, JR & Ralph, PJ 2018, 'An empirical process model to predict microalgal carbon fixation rates in photobioreactors', Algal Research, vol. 31, pp. 334-346.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier B.V. An empirical process model was developed to infer the instantaneous net photosynthesis and carbon fixation rates from continuous pH and dissolved oxygen measurements during microalgal cultivation in photobioreactors. The model is based on the physical and chemical processes that govern the relationship between inorganic carbon supplied to a microalgal culture and the organic carbon fixed into microalgal biomass, with a particular focus on carbonate chemistry and mass transfer. Bayesian statistics were used to estimate the uncertainty in state variables, such as pH, net photosynthesis rate, and bicarbonate ion concentration, based on the constraints imposed by prior knowledge about these variables. The model was verified by batch-culturing the chlorophyte microalga Chlorella vulgaris in a photobioreactor under both bicarbonate-replete and bicarbonate-limiting conditions in order to test its predictive ability under different operational settings. The replicate photobioreactors were set up to simulate a scaled-down vertical cross-section of a typical raceway pond. This model could be used to test the activity and efficiency of carbon concentrating mechanisms in different microalgal species. It also provides a detailed understanding of how the rate of photosynthesis depends on dissolved inorganic carbon concentration, which could lead to better management of carbon supply in large-scale microalgal cultivation facilities.
Zavřel, T, Szabó, M, Tamburic, B, Evenhuis, C, Kuzhiumparambil, U, Literáková, P, Larkum, AWD, Raven, JA, Červený, J & Ralph, PJ 2018, 'Effect of carbon limitation on photosynthetic electron transport in Nannochloropsis oculata.', Journal of photochemistry and photobiology. B, Biology, vol. 181, pp. 31-43.View/Download from: UTS OPUS or Publisher's site
This study describes the impacts of inorganic carbon limitation on the photosynthetic efficiency and operation of photosynthetic electron transport pathways in the biofuel-candidate microalga Nannochloropsis oculata. Using a combination of highly-controlled cultivation setup (photobioreactor), variable chlorophyll a fluorescence and transient spectroscopy methods (electrochromic shift (ECS) and P700 redox kinetics), we showed that net photosynthesis and effective quantum yield of Photosystem II (PSII) decreased in N. oculata under carbon limitation. This was accompanied by a transient increase in total proton motive force and energy-dependent non-photochemical quenching as well as slightly elevated respiration. On the other hand, under carbon limitation the rapid increase in proton motive force (PMF, estimated from the total ECS signal) was also accompanied by reduced conductivity of ATP synthase to protons (estimated from the rate of ECS decay in dark after actinic illumination). This indicates that the slow operation of ATP synthase results in the transient build-up of PMF, which leads to the activation of fast energy dissipation mechanisms such as energy-dependent non-photochemical quenching. N. oculata also increased content of lipids under carbon limitation, which compensated for reduced NAPDH consumption during decreased CO2 fixation. The integrated knowledge of the underlying energetic regulation of photosynthetic processes attained with a combination of biophysical methods may be used to identify photo-physiological signatures of the onset of carbon limitation in microalgal cultivation systems, as well as to potentially identify microalgal strains that can better acclimate to carbon limitation.
Chekli, L, Eripret, C, Park, SH, Tabatabai, SAA, Vronska, O, Tamburic, B, Kim, JH & Shon, HK 2017, 'Coagulation performance and floc characteristics of polytitanium tetrachloride (PTC) compared with titanium tetrachloride (TiCl4) and ferric chloride (FeCl3) in algal turbid water', Separation and Purification Technology, vol. 175, pp. 99-106.View/Download from: UTS OPUS or Publisher's site
© 2016 Elsevier B.V. Seasonal green algae blooms in freshwaters have raised attention on the need to develop novel effective treatment processes for the removal of algae in water. In the present study, the performance of newly developed polytitanium tetrachloride (PTC) coagulant for the removal of freshwater microalga Chlorella vulgaris has been investigated and compared with titanium tetrachloride (TiCl 4 ) coagulant and the conventional ferric chloride (FeCl 3 ) coagulant. The main benefit of using titanium-based coagulants is that the sludge produced after flocculation may be recycled into a valuable product: titanium dioxide photocatalyst. Both titanium-based coagulants achieved good flocculation over a broader pH range and coagulant dose compared to conventional FeCl 3 coagulant. All three coagulants achieved comparable performance in terms of turbidity removal (i.e. turbidity removal efficiency > 97%); although TiCl 4 performed slightly better at the lower tested dose (i.e. < 9 mg/L). Zeta potential measurements indicated that charge neutralisation may not be the sole mechanism involved in the coagulation of algae for all three coagulants. Analysis of the dynamic floc size variation during floc breakage showed no regrowth after floc breakage for the three coagulants. The flocs formed by both Ti-based coagulants were larger than those formed by FeCl 3 and also grew at a faster rate. This study indicates that Ti-based coagulants are effective and promising coagulants for algae removal in water.
Chekli, L, Corjon, E, Tabatabai, SAA, Naidu, G, Tamburic, B, Park, SH & Shon, HK 2017, 'Performance of titanium salts compared to conventional FeCl3 for the removal of algal organic matter (AOM) in synthetic seawater: Coagulation performance, organic fraction removal and floc characteristics.', Journal of Environmental Management, vol. 201, pp. 28-36.View/Download from: UTS OPUS or Publisher's site
During algal bloom periods, operation of seawater reverse osmosis (SWRO) pretreatment processes (e.g. ultrafiltration (UF)) has been hindered due to the high concentration of algal cells and algal organic matter (AOM). The present study evaluated for the first time the performance of titanium salts (i.e. titanium tetrachloride (TiCl4) and polytitanium tetrachloride (PTC)) for the removal of AOM in seawater and results were compared with the conventional FeCl3 coagulant. Previous studies already demonstrated that titanium salts not only provide a cost-effective alternative to conventional coagulants by producing a valuable by-product but also minimise the environmental impact of sludge production. Results from this study showed that both TiCl4 and PTC achieved better performance than FeCl3 in terms of turbidity, UV254 and dissolved organic carbon (DOC) removal at similar coagulant dose. Liquid chromatography - organic carbon detection (LC-OCD) was used to determine the removal of AOM compounds based on their molecular weight (MW). This investigation revealed that both humic substances and low MW organics were preferentially removed (i.e. up to 93% removal) while all three coagulants showed poorer performance for the removal of high MW biopolymers (i.e. less than 50% removal). The detailed characterization of flocs indicated that both titanium coagulants can grow faster, reach larger size and present a more compact structure, which is highly advantageous for the design of smaller and more compact mixing and sedimentation tanks. Both titanium coagulants also presented a higher ability to withstand shear force, which was related to the higher amount of DOC adsorbed with the aggregated flocs. Finally, TiCl4 had a better recovery after breakage suggesting that charge neutralization may be the dominant mechanism for this coagulant, while the lower recovery of both PTC and FeCl3 indicated that sweep flocculation is also a contributing mechanism for the coagulation of AOM...
Commault, AS, Laczka, O, Siboni, N, Tamburic, B, Crosswell, JR, Seymour, JR & Ralph, PJ 2017, 'Electricity and biomass production in a bacteria-Chlorella based microbial fuel cell treating wastewater', Journal of Power Sources, vol. 356, pp. 299-309.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier B.V. The chlorophyte microalga Chlorella vulgaris has been exploited within bioindustrial settings to treat wastewater and produce oxygen at the cathode of microbial fuel cells (MFCs), thereby accumulating algal biomass and producing electricity. We aimed to couple these capacities by growing C. vulgaris at the cathode of MFCs in wastewater previously treated by anodic bacteria. The bioelectrochemical performance of the MFCs was investigated with different catholytes including phosphate buffer and anode effluent, either in the presence or absence of C. vulgaris. The power output fluctuated diurnally in the presence of the alga. The maximum power when C. vulgaris was present reached 34.2 ± 10.0 mW m 2 , double that observed without the alga (15.6 ± 9.7 mW m 2 ), with a relaxation of 0.19 gL 1 d 1 chemical oxygen demand and 5 mg L 1 d 1 ammonium also removed. The microbial community associated with the algal biofilm included nitrogen-fixing (Rhizobiaceae), denitrifying (Pseudomonas stutzeri and Thauera sp., from Pseudomonadales and Rhodocyclales orders, respectively), and nitrate-reducing bacteria (Rheinheimera sp. from the Alteromonadales), all of which likely contributed to nitrogen cycling processes at the cathode. This paper highlights the importance of coupling microbial community screening to electrochemical and chemical analyses to better understand the processes involved in photo-cathode MFCs.
Tran, NAT, Seymour, JR, Siboni, N, Evenhuis, CR & Tamburic, B 2017, 'Photosynthetic carbon uptake induces autoflocculation of the marine microalga Nannochloropsis oculata', Algal Research, vol. 26, pp. 302-311.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier B.V. Microalgal biomass has been used to produce biofuels, aquaculture feed, high-value chemicals such as pigments and antioxidants, and even human food. This study addresses one of the key bottlenecks to the commercialisation of microalgal bioproducts: the high energy and environmental cost of harvesting microalgal cells out of suspension. An innovative and sustainable autoflocculation procedure was developed to pre-concentrate microalgal biomass for easier har vesting. Microalgal cell agglomeration by autoflocculation at high pH was induced for the first time, without the addition of a chemical flocculant, in the commercially-relevant microalga Nannochloropsis oculata. Photosynthetic inorganic carbon uptake, in the absence of carbon dioxide supply by mass transfer, was used to raise the culture pH. Autoflocculation started at pH 9.5 and reached a maximum flocculation efficiency of 90% at pH 10.4. Microalgal surface charge-neutralisation by calcium cations, and sweep flocculation by calcium carbonate and calcium phosphate precipitates were identified as the dominant flocculation mechanisms. This was also the first study to measure changes in bacterial community composition under autoflocculation. There was a clear shift from free-living bacteria in suspension to attached bacteria during autoflocculation, with Flavobacteriales becoming the dominant order of bacteria. This highlights the influential role of attached bacteria and bacteria-produced extracellular polymeric substances in microalgal flocculation. This study shows that regulating carbon dioxide supply is a promising green alternative to traditional microalgal flocculation processes as it alleviates the requirement for costly and harmful chemical flocculants and brings us closer to sustainable microalgal bioproducts.
Tran, NAT, Padula, MP, Evenhuis, CR, Commault, AS, Ralph, PJ & Tamburic, B 2016, 'Proteomic and biophysical analyses reveal a metabolic shift in nitrogen deprived Nannochloropsis oculata', Algal Research, vol. 19, pp. 1-11.View/Download from: UTS OPUS or Publisher's site
© 2016. The microalga Nannochloropsis oculata is a model organism for understanding intracellular lipid production, with potential benefits to the biofuel, aquaculture and nutraceutical industries. It is well known that nitrogen deprivation increases lipid accumulation in microalgae but the underlying processes are not fully understood. In this study, detailed proteomic and biophysical analyses were used to describe mechanisms that regulate carbon partitioning in nitrogen-deplete N. oculata. The alga selectively up- or down-regulated proteins to shift its metabolic flux in order to compensate for deficits in nitrate availability. Under nitrogen deprivation, proteins involved in photosynthesis, carbon fixation and chlorophyll biosynthesis were all down-regulated, and this was reflected in reduced cell growth and chlorophyll content. Protein content was reduced 4.9-fold in nitrogen-deplete conditions while fatty acid methyl esters increased by 60%. Proteomic analysis revealed that organic carbon and nitrogen from the breakdown of proteins and pigments is channeled primarily into fatty acid synthesis. As a result, the fatty acid concentration increased and the fatty acid profile became more favorable for algal biodiesel production. This advancement in microalgal proteomic analysis will help inform lipid accumulation strategies and optimum cultivation conditions for overproduction of fatty acids in N. oculata.
Malik, A, Lenzen, M, Ralph, PJ & Tamburic, B 2015, 'Hybrid life-cycle assessment of algal biofuel production', BIORESOURCE TECHNOLOGY, vol. 184, pp. 436-443.View/Download from: UTS OPUS or Publisher's site
Zhang, D, Chanona, EAD-R, Vassiliadis, VS & Tamburic, B 2015, 'Analysis of green algal growth via dynamic model simulation and process optimization', BIOTECHNOLOGY AND BIOENGINEERING, vol. 112, no. 10, pp. 2025-2039.View/Download from: UTS OPUS or Publisher's site
Tamburic, B, Evenhuis, CR, Suggett, DJ, Larkum, AWD, Raven, JA & Ralph, PJ 2015, 'Gas Transfer Controls Carbon Limitation During Biomass Production by Marine Microalgae', CHEMSUSCHEM, vol. 8, no. 16, pp. 2727-2736.View/Download from: UTS OPUS or Publisher's site
Szabo, M, Parker, KB, Guruprasad, S, Kuzhiumparambil, U, Lilley, RM, Tamburic, B, Schliep, MT, Larkum, A, Schreiber, U, Raven, J & Ralph, PJ 2014, 'Photosynthetic acclimation of Nannochloropsis oculata investigated by multi-wavelength chlorophyll fluorescence analysis', Bioresource Technology, vol. 167, pp. 521-529.View/Download from: UTS OPUS or Publisher's site
Multi-wavelength chlorophyll fluorescence analysis was utilised to examine the photosynthetic efficiency of the biofuel-producing alga Nannochloropsis oculata, grown under two light regimes; low (LL) and high (HL) irradiance levels. Wavelength dependency was evident in the functional absorption cross-section of Photosystem II (sII (?)), absolute electron transfer rates (ETR(II)), and non-photochemical quenching (NPQ) of chlorophyll fluorescence in both HL and LL cells. While sII(?) was not significantly different between the two growth conditions, HL cells upregulated ETR(II) 1.6 to 1.8-fold compared to LL cells, most significantly in the wavelength range of 440-540 nm. This indicates preferential utilisation of blue-green light, a highly relevant spectral region for visible light in algal pond conditions. Under these conditions, the HL cells accumulated saturated fatty acids, whereas polyunsaturated fatty acids were more abundant in LL cells. This knowledge is of importance for the use of N. oculata for fatty acid production in the biofuel industry.
Szabo, M, Wangpraseurt, D, Tamburic, B, Larkum, A, Schreiber, U, Suggett, DJ, Kühl, M & Ralph, PJ 2014, 'Effective light absorption and absolute electron transport rates in the coral Pocillopora damicornis', Plant Physiology and Biochemistry, vol. 83, pp. 159-167.View/Download from: UTS OPUS or Publisher's site
Pulse Amplitude Modulation (PAM) fluorometry has been widely used to estimate the relative photosynthetic efficiency of corals. However, both the optical properties of intact corals as well as past technical constrains to PAM fluorometers have prevented calculations of the electron turnover rate of PSII. We used a new Multi-colour PAM (MC-PAM) in parallel with light microsensors to determine for the first time the wavelength-specific effective absorption cross-section of PSII photochemistry, sII(?), and thus PAM-based absolute electron transport rates of the coral photosymbiont Symbiodinium both in culture and in hospite in the coral Pocillopora damicornis. In both cases, sII of Symbiodinium was highest in the blue spectral region and showed a progressive decrease towards red wavelengths. Absolute values for sII at 440 nm were up to 1.5-times higher in culture than in hospite. Scalar irradiance within the living coral tissue was reduced by 20% in the blue when compared to the incident downwelling irradiance. Absolute electron transport rates of P. damicornis at 440 nm revealed a maximum PSII turnover rate of ca. 250 electrons PSII-1 s-1, consistent with one PSII turnover for every 4 photons absorbed by PSII; this likely reflects the limiting steps in electron transfer between PSII and PSI. Our results show that optical properties of the coral host strongly affect light use efficiency of Symbiodinium. Therefore, relative electron transport rates do not reflect the productivity rates (or indeed how the photosynthesis-light response is parameterised). Here we provide a non-invasive approach to estimate absolute electron transport rates in corals.
Tamburic, B, Szabo, M, Tran, A, Larkum, A, Suggett, DJ & Ralph, PJ 2014, 'Action spectra of oxygen production and chlorophyll a fluorescence in the green microalga Nannochloropsis oculata', Bioresource Technology, vol. 169, pp. 320-327.View/Download from: UTS OPUS or Publisher's site
The first complete action spectrum of oxygen evolution and chlorophyll a fluorescence was measured for the biofuel candidate alga Nannochloropsis oculata. A novel analytical procedure was used to generate a representative and reproducible action spectrum for microalgal cultures. The action spectrum was measured at 14 discrete wavelengths across the visible spectrum, at an equivalent photon flux density of 60 µmol photons m-2 s-1. Blue light (~414 nm) was absorbed more efficiently and directed to photosystem II more effectively than red light (~679 nm) at light intensities below the photosaturation limit. Conversion of absorbed photons into photosynthetic oxygen evolution was maximised at 625 nm; however, this maximum is unstable since neighbouring wavelengths (646 nm) resulted in the lowest photosystem II operating efficiency. Identifying the wavelength-dependence of photosynthesis has clear implications to optimising growth efficiency and hence important economic implications to the algal biofuels and bioproducts industries.
Tamburic, B, Guruprasad, S, Radford, DT, Szabo, M, Lilley, R, Larkum, A, Franklin, J, Kramer, D, Blackburn, S, Raven, J, Schliep, MT & Ralph, PJ 2014, 'The effect of diel temperature and light cycles on the growth of Nannochloropsis oculata in a photobioreactor matrix', PLoS One, vol. 9, no. 1, p. e86047.View/Download from: UTS OPUS or Publisher's site
Tamburic, B, Dechatiwongse, P, Zemichael, FW, Maitland, GC & Hellgardt, K 2013, 'Process and reactor design for biophotolytic hydrogen production', Physical Chemistry Chemical Physics, vol. 15, no. 26, pp. 10783-10794.View/Download from: UTS OPUS or Publisher's site
The green alga Chlamydomonas reinhardtii has the ability to produce molecular hydrogen (H2), a clean and renewable fuel, through the biophotolysis of water under sulphur-deprived anaerobic conditions. The aim of this study was to advance the development of a practical and scalable biophotolytic H2 production process. Experiments were carried out using a purpose-built flat-plate photobioreactor, designed to facilitate green algal H2 production at the laboratory scale and equipped with a membrane-inlet mass spectrometry system to accurately measure H2 production rates in real time. The nutrient control method of sulphur deprivation was used to achieve spontaneous H2 production following algal growth. Sulphur dilution and sulphur feed techniques were used to extend algal lifetime in order to increase the duration of H2 production. The sulphur dilution technique proved effective at encouraging cyclic H2 production, resulting in alternating Chlamydomonas reinhardtii recovery and H2 production stages. The sulphur feed technique enabled photobioreactor operation in chemostat mode, resulting in a small improvement in H2 production duration. A conceptual design for a large-scale photobioreactor was proposed based on these experimental results. This photobioreactor has the capacity to enable continuous and economical H2 and biomass production using green algae. The success of these complementary approaches demonstrate that engineering advances can lead to improvements in the scalability and affordability of biophotolytic H2 production, giving increased confidence that H2 can fulfil its potential as a sustainable fuel of the future.
Patel, B, Tamburic, B, Zemichael, FW, Dechatiwongse, P & Hellgardt, K 2012, 'Algal Biofuels: A Credible Prospective?', ISRN Renewable Energy, vol. 2012, no. 1, pp. 1-14.View/Download from: UTS OPUS or Publisher's site
Global energy use has reached unprecedented levels and increasing human population, technological integration, and improving lifestyle will further fuel this demand. Fossil fuel based energy is our primary source of energy and it will remain to be in the near future. The effects from the use of this finite resource on the fate of our planet are only now being understood and recognised in the form of climate change. Renewable energy systems may offer a credible alternative to help maintain our lifestyle sustainably and there are a range of options that can be pursued. Biofuels, especially algae based, have gained significant publicity recently. The concept of making biofuels, biochemicals, and by-products works well theoretically and at small scale, but when considering scaleup, many solutions can be dismissed on either economical or ecological grounds. Even if an (cost-) effective method for algae cultivation is developed, other input parameters, namely, fixed nitrogen and fresh water, remain to be addressed. Furthermore, current processing routes for harvesting, drying, and extraction for conversion to subsequent products are economically unattractive. The strategies employed for various algae-based fuels are identified and it is suggested that ultimately only an integrated algal biorefinery concept may be the way forward.
Tamburic, B, Zemichael, FW, Maitland, GC & Hellgardt, K 2012, 'A novel nutrient control method to deprive green algae of sulphur and initiate spontaneous hydrogen production', International Journal of Hydrogen Energy, vol. 37, no. 11, pp. 8988-9001.View/Download from: UTS OPUS or Publisher's site
The green alga Chlamydomonas reinhardtii has the ability to produce clean and renewable molecular hydrogen through the biophotolysis of water. Hydrogen production takes place under anaerobic conditions, which may be imposed metabolically by depriving the algae of sulphur. Sulphur-deprivation typically requires the spatial and temporal separation of the algal growth and hydrogen production stages. This would typically require separate photobioreactors for each stage as well as a costly and energy intensive medium exchange technique such as centrifugation, making the process difficult to scale up. The aim of this paper is to show how these two stages are able to take place in a single reactor and hence eliminate the need for a separation step and for an additional reactor. To achieve this we have investigated the sulphate and acetate consumption and uptake rates during algal growth under different illumination conditions. The experiment has been repeated in various photobioreactor geometries in order to determine a reactorindependent relationship between the algal growth and nutrient consumption kinetics. Using this relationship, the initial sulphur and acetate concentrations of the algal medium have been optimised so that these nutrients run out at the exact moment when the maximum algal cell density is reached. This nutrient control method allows a fully-grown algal culture to enter spontaneous hydrogen production mode, eliminating the need for a medium separation technique and for an additional photobioreactor. Hydrogen production rates and yields were measured by membrane-inlet mass spectrometry (MIMS) in a novel photobioreactor designed specifically to facilitate the green algal hydrogen production process. The nutrient control method of sulphur-deprivation has proven to be superior to the traditional methods of centrifugation and dilution. Hydrogen production by nutrient control reached a maximum rate of 1.30 ml/l/h and a yield of 112.7 ml/l, compared to maxi...
Tamburic, B, Zemichael, FW, Maitland, GC & Hellgardt, K 2012, 'Effect of the light regime and phototrophic conditions on growth of the H2-producing green alga Chlamydomonas reinhardtii', Energy Procedia, vol. 29, pp. 710-719.View/Download from: UTS OPUS or Publisher's site
Development of the capacity to produce hydrogen economically from renewable energy resources is of critical importance to the future viability of that fuel. The inexpensive and widely available green alga Chlamydomonas reinhardtii has the ability to photosynthetically synthesise molecular hydrogen. Green algal hydrogen production does not generate any toxic or polluting bi-products and could potentially offer value-added products derived from algal biomass. The growth of dense and healthy algal biomass is a vital requirement for efficient hydrogen production. Algal cell density is principally limited by the illumination conditions of the algal culture and by the availability of key nutrients, including the sources of carbon, nitrogen, sulphur and phosphorus. In this study, the effect of different light regimes and carbon dioxide feeds on Chlamydomonas reinhardtii growth were investigated. The objective was to increasing the algal growth rate and the cell density, leading to enhanced biohydrogen production. State-of-the art photobioreactors were used to grow algal cultures, and to measure the pH and optical density of those cultures. Under mixotrophic growth conditions, using both acetate and carbon dioxide, increasing the carbon dioxide feed rate increased the optical density of the culture but reduced the growth rate. Under autotrophic growth conditions, with carbon dioxide as the only carbon source, a carbon dioxide feed with a partial pressure of circa 11% was determined to optimise both the algal growth rate and the optical density.
Burgess, SJ, Tamburic, B, Zemichael, FW, Hellgardt, K & Nixon, PJ 2011, 'Solar-driven hydrogen production in green algae', Advances in Applied Microbiology, vol. 75, no. 1, pp. 71-110.View/Download from: UTS OPUS or Publisher's site
The twin problems of energy security and global warming make hydrogen an attractive alternative to traditional fossil fuels with its combustion resulting only in the release of water vapor. Biological hydrogen production represents a renewable source of the gas and can be performed by a diverse range of microorganisms from strict anaerobic bacteria to eukaryotic green algae. Compared to conventional methods for generating H2, biological systems can operate at ambient temperatures and pressures without the need for rare metals and could potentially be coupled to a variety of biotechnological processes ranging from desalination and waste water treatment to pharmaceutical production. Photobiological hydrogen production by microalgae is particularly attractive as the main inputs for the process (water and solar energy) are plentiful. This chapter focuses on recent developments in solar-driven H2 production in green algae with emphasis on the model organism Chlamydomonas reinhardtii. We review the current methods used to achieve sustained H2 evolution and discuss possible approaches to improve H2 yields, including the optimization of culturing conditions, reducing light-harvesting antennae and targeting auxiliary electron transport and fermentative pathways that compete with the hydrogenase for reductant. Finally, industrial scale-up is discussed in the context of photobioreactor design and the future prospects of the field are considered within the broader context of a biorefinery concept.
Tamburic, B, Zemichael, FW, Crudge, P, Maitland, GC & Hellgardt, K 2011, 'Design of a novel flat-plate photobioreactor system for green algal hydrogen production', International Journal of Hydrogen Energy, vol. 36, no. 11, pp. 6578-6591.View/Download from: UTS OPUS or Publisher's site
Some green microalgae have the ability to harness sunlight to photosynthetically produce molecular hydrogen from water. This renewable, carbon-neutral process has the additional benefit of sequestering carbon dioxide and accumulating biomass during the algal growth phase. We document the details of a novel one-litre vertical flat-plate photobioreactor that has been designed to facilitate green algal hydrogen production at the laboratory scale. Coherent, non-heating illumination is provided by a panel of cool-white light-emitting diodes. The reactor body consists of two compartments constructed from transparent polymethyl methacrylate sheets. The primary compartment holds the algal culture, which is agitated by means of a recirculating gas-lift. The secondary compartment is used to control the temperature of the system and the wavelength of radiation. The reactor is fitted with probe sensors that monitor the pH, dissolved oxygen, temperature and optical thickness of the algal culture. A membrane-inlet mass spectrometry system has been developed and incorporated into the reactor for dissolved hydrogen measurement and collection. The reactor is hydrogen-tight, modular and fully autoclaveable.
Tamburic, B, Zemichael, FW, Maitland, GC & Hellgardt, K 2011, 'Parameters affecting the growth and hydrogen production of the green alga Chlamydomonas reinhardtii', International Journal of Hydrogen Energy, vol. 36, no. 13, pp. 7872-7876.View/Download from: UTS OPUS or Publisher's site
The green alga Chlamydomonas reinhardtii has the ability to photosynthetically produce molecular hydrogen (H2) under anaerobic conditions. It offers a biological route to renewable H2 production from sunlight and water. Algal growth and H2 production kinetics must be understood in order to determine appropriate system parameters and develop photobioreactors. Algal biomass should be grown efficiently and economically to attain the high cell densities necessary forH2 production. The nutrient requirements and process conditions that encourage the growth of dense and healthy algal cultures were explored. Anaerobic conditions were imposed by sulphur deprivation, which requires an exchange of the algal growth medium by centrifugation or dilution. A tubular flow photobioreactor featuring a large surface-to-volume ratio was used tomonitor and control the key parameters in theH2 production process, including pH, dissolved oxygen, optical density, temperature, agitation and light intensity. A cumulative H2 yield of 3.1 0.3 ml/l of culture was measured.