Maximum Lipid Productivity Research Articles

Biochemical analysis and potential applications of aqueous and solid products generated from subcritical water extraction of microalgae Chlorella pyrenoidosa biomass

Subcritical water extraction (SWE) technology has become useful as a green extraction technology for generating various biochemical and bioactive compounds from a wide range of biomass feedstocks, including microalgae. SWE processes result in two different product phases: an aqueous phase containing solubilized or immiscible bioactive compounds from the extract, and solid-phase biomass debris containing residual or unextracted bioactive molecules in the matrix. While most SWEs of microalgal biomass focus on maximizing lipid production for biofuel application, the present work seeks to explore opportunities to identify and characterize compounds obtained from both the aqueous and solid phases. SWE of Chlorella pyrenoidosa biomass was carried out under varying conditions of temperature (170–370 °C), extraction time (1–20 min), and microalgal biomass loading (1–15%). Analysis of aqueous and solid-phase samples collected under varying SWE conditions showed a higher protein concentration of 4.13 mg mL−1 in the aqueous phase compared with carbohydrate (1.35 mg mL−1) for the optimum extraction conditions. About 17.52 mg g−1 of amino acids and 12.72 mg g−1 of organic acids were obtained from the aqueous phase with glutamic acid and lactic acid being the highest. The findings from this work would be useful in identifying and harnessing important microalgal biochemical from SWE process to develop new and improved bioproduct technologies.

Specific uptake kinetics of glucose and nitrate in carbon-limited and nitrogen-limited C:N ratio under photoheterotrophic cultural conditions for Botryococcus brauniigrowth and lipid production

Carbon and nitrogen are the most significant parameters for microalgal growth and an effective C:N ratio is critical to assess the biomass and lipid productivities of Botryococcus braunii. In this study, the effect of the C:N ratio on specific uptake kinetics of glucose and nitrate was evaluated using substrate kinetic equation, under glucose limited and nitrate limited photoheterotrophic conditions. In glucose limited conditions, the maximum specific growth rate, biomass and lipid productivity of 0.0873 h−1, 1.11 g L−1 d−1 and 0.390 g L−1 d−1 were observed respectively for C:N ratio of 29:1. Maximum specific nitrate uptake rate of 0.190 mM gb−1 h−1 was observed under glucose limited C:N ratio of 61:1 (i.e. carbon sufficient), while the maximum glucose uptake rate of 0.74 mM gb−1 h−1 was observed in nitrate limited C:N ratio of 13:1 (i.e. nitrogen sufficient). This suggests that carbon and nitrogen metabolism is linked together and significantly affects the specific uptake kinetics of the each other.

Use of magnetic fields and nitrate concentration to optimize the growth and lipid yield of Nannochloropsis oculata

Microalgae produce increased lipid content accompanied by a significant decrease in cell density with decreasing nitrate concentration. Magnetic fields (MF) have been reported as a factor that could accelerate metabolism and growth in microalgae culture. Thus, this study aimed to optimize the influence of MF and nitrate concentration (sodium nitrate, N) on the growth and lipid productivity of Nannochloropsis oculata. A single-factor experiment integrated with response surface methodology (RSM) via central composite design (CCD) was performed. The results showed that the maximum specific growth rate (0.24 d−1) and maximum lipid productivity (38 mg L−1 d−1) obtained in this study were higher than those of the control culture (by 166% and 103%, respectively). This study also found that the two-way interaction term MF × N had a significant effect on cell growth but not on lipid production. It was concluded that to design appropriate MF for enhanced lipid productivity due to cell growth, further research must focus on developing an understanding of the relationship between the bioeffects of the magnetic field and the proteomic changes involved in lipid accumulation strategies. This approach would enable the design of conditions to obtain inexpensive high-value products from N. oculata.

Optimization of biomass and fatty acid productivity of Desmodesmus intermedius as a promising microalga for biodiesel production

ABSTRACT The present study aimed to optimize the culture conditions for algal growth and lipid production of Desmodesmus intermedius. Different environmental factors including nitrogen content, salinity, kinetin hormone, vitamin B12, and light intensity were applied individually or in combination using Plackett–Burman statistical experimental design. In addition, the impact of optimized conditions on fatty acids profile and biodiesel quality was studied. Results revealed that the maximum lipid and biomass production for individual study optimization was recorded using 125 mg/L sodium nitrate, 12.5 mg/L sodium chloride, 10−7 mol/L kinetin, and 10−2 mg/L vitamin B12, at 4500 lux. In addition, Plackett-Burman model revealed that combination of sodium nitrate (125 mg/L), sodium chloride (25 mg/L), Kinetin hormone (0 mol/L), vitamin B12 (0 mg/L), and Light intensity (4500 Lux) resulted in maximum lipid productivity. The overall enhancements in lipid productivities using Plaktt–Berman model were 20% and 61.6% over individual optimization and control, respectively. Fatty acids profile for D. intermedius recorded the presence of 14 fatty acids. These fatty acids are suitable to produce high-quality biodiesel.

Influence of nutrient supplementation and starvation conditions on the biomass and lipid productivities of Micractinium reisseri grown in wastewater for biodiesel production

Generation of biodiesel from microalgae grown in wastewater can offer a cost-effective approach, whilst wastewaters usually do not contain the optimum concentrations of the essential nutrients and carbon sources that result in lowering the productivities of biomass and lipid. This study aimed to overcome this limitation by manipulating wastewater with various concentrations of nutrients (NO3−, PO43−, Cl− and SO42−) and three carbon sources either individually or in combination to cultivate Micractinium reisseri for biodiesel production. Initially, various dilutions of wastewater were tested and a concentration up to 75% of wastewater showed the highest biomass productivity (0.076 g L−1 d−1) and lipid productivity (0.014 g L−1 d−1). The optimum manipulating conditions for maximum lipid production and the highest productivity required 50% decrease in phosphorous from the concentration of the control medium and supplementation with 1.0 g L−1 of glucose. Under this condition, biomass and lipid productivities increased by 1.7 and 4-folds, respectively, compared to those observed in the control. Furthermore, phosphorous starvation condition in the presence of glucose significantly improved fatty acid profile in the biomass and biodiesel quality related parameters.

Relating nitrogen concentration and light intensity to the growth and lipid accumulation of Dunaliella viridis in a photobioreactor

The marine microalgal species Dunaliella viridis is a promising source of biofuels because of its ability to accumulate neutral lipids without freshwater resources for growth. Less energy for biofuel production from D. viridis may also be required because of the possible extraction of lipids through osmotic lysis. However, there is a lack of experimental data on the growth of D. viridis that can be used in mathematical models for process design. In this study, experiments were performed in a 3.2 L photobioreactor with both pH and temperature tightly controlled at 7.6 and 25 °C, respectively. Levels of neutral lipids, biomass, carbohydrate, chlorophyll, and cell counts of D. viridis were evaluated for ten days at various initial light intensities (100, 300, 400, and 600 μmol photons m−2 s−1) and nitrogen levels (9 and 60 g m−3 as nitrogen). The maximum lipid production observed was 26.9 g m−3 with 3.15 g m−3 day−1 average lipid productivity at an initial nitrogen concentration of 9 g m−3 and initial light intensity of 300 μmol photons m−2 s−1. The data show that D. viridis accumulates cellular carbohydrates as a primary carbon and energy storage product and then converts the cellular carbohydrates into cellular lipids as a secondary storage product when nitrogen is depleted. The on-line light data revealed linear relationships between real-time light intensity and biomass concentration (r = 0.96, p < 0.01) and between real-time light intensity and chlorophyll a concentration (r = − 0.89, p < 0.01), suggesting the possible use of real-time light data as a method for in situ quantification of biomass concentration and chlorophyll a concentration.

Enhancing Stability of Microalgae Biocathode by a Partially Submerged Carbon Cloth Electrode for Bioenergy Production from Wastewater

The electricity output from microbial fuel cell (MFC) with a microalgae assisted cathode is usually higher than that with an air cathode. The output of electricity from a photosynthetic microalgae MFC was positively correlated with the dissolved oxygen (DO) level in the microalgae assisted biocathode. However, DO is highly affected by the photosynthesis of microalgae, leading to the low stability in the electricity output that easily varies with the change in microalgae growth. In this study, to improve the electricity output stability of the MFC, a partially submerged carbon cloth cathode electrode was first investigated to use oxygen from both microalgae and air, with synthetic piggery wastewater used as the anolyte and anaerobically digested swine wastewater as the catholyte. When the DO levels dropped from 13.6–14.8 to 1.0–1.6 mg/L, the working voltages in the MFCs with partially submerged electrodes remained high (256–239 mV), whereas that for the conventional completely submerged electrodes dropped from 259 to 102 mV. The working voltages (average, 297 ± 26 mV) of the MFCs with the 50% submerged electrodes were significantly (p &lt; 0.05) higher than with other partially or completely submerged electrodes. The associated maximum lipid production from wastewater was 250 ± 42 mg/L with lipid content of 41 ± 6% dry biomass. Although the partially submerged electrode had no significant effects on lipid production or nitrogen removal in wastewater, there was significant improvement in the stability of the electricity generated under variable conditions.

In-pond strain selection of euryhaline Tetraselmis sp. strains for reliable long-term outdoor culture as potential sources of biofuel and other products

Studies on microalgae species and strain selection have demonstrated the potential of a broad range of algal species suitable for large-scale mass production, but provided little data on the reliability and productivity of the cultures under outdoor conditions over a long period. Long-term studies as part of the development of large-scale microalgae mass production are essential at small scale to minimise expenditure in scaling-up and large-scale operations. The current study describes the long-term semi-continuous culture of 4 wild-type isolates of euryhaline Tetraselmis sp. grown in 1 m2 raceway ponds outdoors in 7% (w/w NaCl) saline water enriched with N and P without any additional carbon source under the environmental conditions in Perth, Western Australia. The long-term investigation indicated that Tetraselmis MUR-231 was not able to grow outdoors, while Tetraselmis strains MUR-167, MUR-230 and MUR-233 grew outdoors over long periods. Tetraselmis MUR-167 was cultured for over 16 months outdoors before terminated due to cell clump formation and heavy biofilm development on the pond walls, whereas Tetraselmis strains MUR-230 and MUR-233 were cultured in semi-continuous culture over 20 months. The latter two strains grew at high solar irradiance with daily maximum values of 58890 W m−2 and temperatures ranging from about 40 to 0 °C. Both strains had a similar average specific growth rate of 0.19 day−1 over the experimental period. Maximum biomass productivities were 9.11 g m−2 day−1 and 9.99 g m−2 day−1 for Tetraselmis MUR-230 and MUR-233, respectively. The maximum total lipid productivity of 4.30 g m−2 day−1 of Tetraselmis MUR-230 was slightly higher than Tetraselmis MUR-233 (4.05 g m−2 day−1). These results clearly indicate the potential of these two Tetraselmis strains for commercial application, such as a high lipid yielding feedstock under minimal culture management conditions in arid and semi-arid coastal regions such as northern Western Australia.

Microbial Lipid Accumulation through Bioremediation of Palm Oil Mill Wastewater by Bacillus cereus

The wastewater burden and increased energy demands have spurred interest in finding possible solutions that could concomitantly address both issues. Microbial lipid production, together with the bioremediation of wastewater, could be a promising solution to address both problems. In this context, the present study was designed to evaluate the potential of Bacillus cereus (B. cereus) for accumulating microbial lipids through the bioremediation of palm oil mill effluent (POME) in batch mode fermentation. Different dilutions of POME media (25%, 50%, 75%, and 100%) were used to determine the optimum POME concentration for enabling the maximum yield of biomass and maximum lipid production. The 50% (v/v) POME was found to have potential for the highest biomass growth (8.09 g/L) and lipid accumulation (1.46 g/L), with a lipid content of 18.04% (dry weight basis). B. cereus accumulated a higher biomass and lipid content than other bacterial strains, such as Rhodococcus opacus and Pseudomonas aeruginosa, under similar conditions. On the other hand, the degree of bioremediation was assessed by evaluating several wastewater parameters and determining the seed germination index (GI) of Vigna radiata. POME treated with B. cereus displayed higher GI values than the untreated samples due to the significant remediation of detrimental organics present in the POME. This finding was further confirmed by the substantial reduction in pollution load, particularly in chemical oxygen demand (COD) and biochemical oxygen demand (BOD) for 50% POME, thus demonstrating removal efficiencies of 79.35% and 72.65%, respectively. Therefore, the results of this study suggest that B. cereus cultivation in POME could be a promising technique for attaining higher biomass growth and lipid production in conjunction with the bioremediation of POME. The approach of achieving dual objectives that is utilized in the present study provides a novel strategy for palm oil millers.

The effect of medium and light wavelength towards Stichococcus bacillaris fatty acid production and composition

Introduction of novel species will highlight technical feasibility of microalgae-based biofuels for commercial applications. This paper reports the effect of culture medium and light wavelength on biomass and fatty acid production of S. bacillaris which holds some advantages as short life cycle, easy cultivation, high lipid content, diversity of fatty acids and stability under harsh environmental conditions. The results displayed that, soil extract (SE) greatly enhance growth rate of cultures. Maximum biomass and lipid productivity were achieved in TAP medium as 81 mg/L·day, 19.44 mg/L·day; respectively. Light wavelength didn’t significantly change growth kinetics but played a critical role on chlorophyll-a accumulation. C14:0, C16:0 and C18:0 fatty acids were abundant which are suitable for biodiesel conversion. Interestingly, blue and red light increased longer chain fatty acids content. These results indicated that; S. bacillaris holds potential for further development of biodiesel production and feasibility of algal biodiesel for fundamental and applied sciences.

Accelerated lipid production from distillery wastewater by Rhodosporidium toruloides using an open-bubble-column reactor under non-aseptic conditions

It is an ideal and sustainable approach to recover renewable energy like biodiesel and to remove organic matters from wastewater simultaneously. However, the common demands of aseptic conditions and long reaction time limit the practical applications of this technology. In this study, lipid production by Rhodosporidium toruloides was investigated using distillery wastewater with an initial soluble chemical oxygen demand (SCOD) of 28,080–17,120 mg/L, an initial cell density of 0.5–2 × 108 cells/mL, and an aeration rate of 0.9–4.5 vvm (air volume/liquid volume/minute) in an open-bubble-column reactor at room temperature. The lipid production reached its peak of 1.92 ± 0.24 g/L in 12 h with a maximum lipid productivity of 160 mg/(L• h) achieved under the conditions: initial SCOD 20,315 mg/L, initial cell density 2 × 108 cells/mL and aeration rate 4 vvm, without external nutrients and sterilization. The associated removal efficiencies for SCOD, total phosphorus (TP) and total nitrogen (TN) were 71.82 ± 0.52%, 79.53 ± 1.77% and 54.39 ± 6.45%, respectively. Both contaminating bacteria and fungi were negligible throughout the cultivation period, suggesting that the studied process has good adaptability to full scale practical applications.

Species disparity response to mutagenesis of marine yeasts for the potential production of biodiesel

BackgroundAmong the third-generation biodiesel feed stock, oleaginous marine yeasts are the least studied microorganisms for such purpose.ResultsWild strains yeasts were isolated from various Tunisian marine sources including fish waste (Candida tenuis CtTun15, Debaryomyces hansenii DhTun2015, Trichosporon asahii TaTun15 and Yarrowia lipolytica YlTun15) and seawater (Rhodotorula mucilaginosa RmTun15). Following incubation with ethyl methanesulfonate (EMS: 75 mM) for various periods of time (T15, T30, T45, T60 min), the cell viability of these strains responded differentially according to yeast species. For instance, mutated CtTun15 did not survive after 30 min of EMS treatment; higher resistances were observed in DhTun2015 (45 min), in YlTun15, RmTun15 and in TaTun15 (60 min) but with significant decreased cell viabilities (survival rate: 6.02, 3.16, 11.22, 11.58, 7.70%, respectively). For all surviving mutated strains, the optima of biomass and lipid yields were detected after 96 h in YPD culture; but derived from strains submitted to different period of EMS incubation. In most mutated strains, the maximum biomass (BP) and lipid (LP) productivities coincided and were observed after 30 min of EMS incubation. Only CtTun15 showed different optima of BP and LP (after 30 min and 15 min, respectively). The fatty acids (FA) compositions considered essential in the prediction of biodiesel criteria; were highly affected by EMS mutagenesis. Essentially, 30- and 45-min EMS incubation induced the highest levels of PUFA and MUFA in YlTun15, RmTun15 and TaTun15 with non-significant differences in the different times. However, CtTun15 and DhTun2015 mutant strains responded differently, with the highest levels of MUFA observed following 15 and 45 min; and that of PUFA after 30 and 45 min, respectively.ConclusionThe methyl-esterification of FA from the three mutated yeast strains (30 min—YlTun15, RmTun15 and TaTun15) yielded biodiesel with physical proprieties consistent with the International Standard System. However, investigations are needed for up-scaling biodiesel production.

Optimization of microalgal growth and cultivation parameters for increasing bioenergy potential: Case study using the oleaginous microalga Chlorella pyrenoidosa Chick (IPPAS C2)

The aim of the presented research was application of optimized cultivation conditions for lipid production using the oleaginous microalga Chlorella pyrenoidosa Chick (IPPAS C2), followed by an assessment of the bioenergy potential of lipid-rich biomass and biomethane production. The optimization of cultivation parameters led to an increase in lipid production. The average and maximum lipid production for C. pyrenoidosa was 101 ± 22 mg.L−1.D−1 and 126 mg.L−1.D−1, respectively. The average calorific value of the lipid rich-biomass was 27.56 ± 0.93 MJ.kg−1. However, the recorded biomethane yield of 0.16 ± 0.006 m3.kg−1 VS, caused probably by low digestibility of C. pyrenoidosa and by short hydraulic retention time during anaerobic digestion, was interpreted as low. However, the high lipid content along with high calorific value indicated an increased bioenergy potential of microalgal biomass cultivated under the optimized cultivation parameters.

Lipid production from indigenous Greek microalgae: a possible biodiesel source.

Microalgae gained interest for potential use as biodiesel producers, since they synthesize and accumulate significant quantities of lipids. The aim of this work was to isolate indigenous microalgae strains from Greek habitats, study their physicochemical growth conditions and finally select the best ones with respect to overall lipid production and profile. Two sampling sites of marine aquatic ecosystems were selected in Attica prefecture, Greece in order to screen for novel wild type strains with lipid production capacity. Microalgae isolates (59) were obtained from the selected areas and were morphologically and molecularly characterized. Fatty acids were estimated through Flow Cytometry combined with BODIPY staining method. Four isolates were selected for their lipid production properties and were cultivated in 15 L tank cultures. The four isolates were also identified by 18S rDNA gene sequencing. Two of them, Chlorella sp. ΑCΑ9 and ACA17, exhibited both maximum biomass and lipid productivity. Optimization of growth conditions with respect to pH and initial NaNO3 concentration was performed for the two microalgae in 15 L cultures. Finally, 20 L fed batch cultures were set up using the optimum culture conditions. Lipid profiles were stabilized for both strains at dry biomass levels over 1gL-1 and lipid content of 25% (w/w). Two Chlorella strains (ACA9 andACA17) were promising candidates for biodiesel production as they were easily grown in sea water in fed batch systems and produce lipids suitable for biodiesel-especially Chlorella sp. ACA9.

Exploring the potency of integrating semi-batch operation into lipid yield performance of Chlamydomonas sp. Tai-03

Third generation biofuels, also known as microalgal biofuels, are promising alternatives to fossil fuels. One attractive option is microalgal biodiesel as a replacement for diesel fuel. Chlamydomonas sp. Tai-03 was previously optimized for maximal lipid production for biodiesel generation, achieving biomass growth and productivity of 3.48 ± 0.04 g/L and 0.43 ± 0.01 g/L/d, with lipid content and productivity of 28.6 ± 1.41% and 124.1 ± 7.57 mg/L/d. In this study, further optimization using 5% CO2 concentration and semi-batch operation with 25% medium replacement ratio, enhanced the biomass growth and productivity to 4.15 ± 0.12 g/L and 1.23 ± 0.02 g/L/d, with lipid content and productivity of 19.4 ± 2.0% and 239.6 ± 24.8 mg/L/d. The major fatty acid methyl esters (FAMEs) were palmitic acid (C16:0), oleic acid (C18:1), and linoleic acid (C18:2). These short-chain FAMEs combined with high growth make Chlamydomonas sp. Tai-03 a suitable candidate for biodiesel synthesis.

Simultaneous induction of biomass and lipid production in Tetradesmus obliquus BPL16 through polysorbate supplementation

The strategic microalgal lipid production without growth reduction is the desideratum for sustainable microalgal biodiesel production. The present study investigated the effect of polysorbates (polysorbate 20, polysorbate 40, polysorbate 60 & polysorbate 80) supplementation on growth, biomass and lipid production of microalga Tetradesmus obliquus BPL16. T. obliquus BPL16 at controlled condition showed 12.5% dry cell weight (DCW) of lipid content and 0.8 g L−1 of biomass production. Each of the four tested polysorbates at various concentrations magnificently influenced the green microalga with a maximum lipid production of 47.1% DCW and 46.5% DCW achieved at 0.15% of polysorbate 80 and 0.1% of polysorbate 60 supplementations respectively. The maximum biomass (2.6 g L−1) production was achieved at 0.15% of polysorbate 40 and polysorbate 60 supplementation respectively. In addition, neutral lipids and vital fatty acids proportion increased at high lipid productive conditions enabled by polysorbate supplementation.

Microalgae as a Source of Functional PUFAs: A Green Low-cost Pathway via Enzymatic Hydrolysis

Microalgal oil is an alternative source of polyunsaturated fatty acids (PUFAs) that can replace conventional ones such as vegetable and fish oils. In this work, Nannochloropsis gaditana oil was investigated as a source of high-value polyunsaturated fatty acids.&#x0D; The cultivation conditions were optimized using a 22 full factorial design to simultaneously assess the influence of NaNO3 (0.075 to 0.225 mg.L-1) and CH3COONa (2 to 6 g.L-1) concentrations on the lipid productivity. All cultivations were done in 4 L tank photo bioreactors for 7 days, yielding 21.87 mg.L-1.day-1 maximum lipid productivity when using 225 mg.L-1 of nitrate and 6 g.L-1 of acetate. The obtained microbial oil was further characterized revealing palmitic (22.1%), oleic (22.3%), and linoleic (17.0%) as the main fatty acids. The resulting microbial oil was employed in the hydrolysis reactions and different sources of lipases as biocatalysts. The highest performance was achieved by the lipases Burkholderia cepacia (86%), Candida rugosa (84%), and Rhizopus oryzae (82%).

Qualitative biodiesel production from a locally isolated chlorophycean microalga Scenedesmus obliquus (Turpin) Kützing GA 45 under closed raceway pond cultivation

The energy security scenario in the world would remain at high risk until non-conventional, indigenously produced renewable biofuels replace/supplement petroleum-based conventional fossil fuels. In the present study, an indigenously isolated chlorophycean microalga, Scenedesmus obliquus (Turpin) Kützing GA 45, was explored under raceway pond cultivation to assess its potential for production of lipids for qualitative biodiesel purpose. Microalgal cultivation was carried out in closed raceway ponds (14 × 4 × 0.75 m) with a capacity of 40,000 L each. The maximum areal biomass and lipid productivities were recorded to be 13.12 and 1.39 g m−2 day−1 at 30 cm culture depth during winter season followed by summer and rainy seasons. Under biphasic nitrogen starvation strategy, the maximum lipid productivity increased up to 2.29, 1.88, and 2.43 g m−2 day−1, respectively during summer, rainy, and winter seasons. The average lipid productivity was consequently calculated to be 2.2 g m−2 day−1, thus projecting an approximate annual lipid productivity of 7.04 t ha−1 y−1, assuming 10 cultivation cycles per year. Characterization of various fuel properties of the biodiesel produced, were found to be within the specified limits of national and international biodiesel standards, thus signifying the potential of the new isolate S. obliquus GA 45 for qualitative biodiesel production.

Nitrogen modulation under chemostat cultivation mode induces biomass and lipid production by Chlorella vulgaris and reduces antenna pigment accumulation

Algal growth limitation in large-scale cultivation mostly results from high level synthesis of photosynthetic pigments, owing to self-shading effects and attenuation of light distribution. To overcome this problem, here we investigated the influence of nitrogen modulation on changes in antenna pigments as well as biomass and lipid production by Chlorella vulgaris under a chemostat continuous cultivation mode. The production of algal antenna pigments, including chlorophylls and carotenoids, was promoted in a total nitrogen (TN) concentration-dependent manner. Maximum algal biomass and lipid production were obtained from 70 mg/L of TN concentration along with a significant increase in light transmittance and reduction in antenna pigments. Furthermore, the composition of polyunsaturated fatty acids remarkably augmented at low TN concentrations. These results suggest that the reduction in algal antenna pigment synthesis via modulation of nitrogen concentration may serve as an effective strategy to enhance algal biomass and lipid production.

Online estimation of biomass, lipid and nitrate dynamic profile using innovative light evolution kinetic model in flat panel airlift photobioreactor for Botryococcus braunii under varying light conditions

Light availability inside the photobioreactor is generally measured by the Lambert – Beer law. However, Lambert - Beer law assumptions are not valid at high cell density cultural conditions, because light scattering and differential absorption have significant impact on light transfer in photobioreactor. In this study Lambert – Beer law was modified by applying differential absorbance in flat panel photobioreactor. As light intensity fluctuate with location and age in the cultivation process, aconsolidated model based on Lambert – Beer law including temporal light evolution and microorganism growth is presented. The model was calibrated under specific light intensity of 133 μmol m−2 s−1 and validated using the experimental data of microalgae growth under varying light conditions of 174, 261 and 348 μmol m−2 s−1. Maximum biomass concentration, maximum lipid content and lipid productivity were 2.52 g dcw L−1, 19.76% and 114.92 mg L−1d−1 at 261 μmol m−2 s−1 light intensity respectively.