Maximum Lipid Productivity Research Articles

Potential of enzymatically hydorlysed seaweed products as cost-effective nutrient media for growth and lipid enhancement in the marine microalga Nannochloropsis salina

Enzymatically hydrolysed seaweed products (EHSPs) prepared from the red seaweed, Gracilaria corticata (EHSP-1) and brown seaweed, Stoechospermum marginatum (EHSP-2) contained abundant levels of macro, micro and trace elements necessary to fulfil the nutritional requirement of the microalga Nannochloropsis salina. EHSP-1 had higher levels of N, P, K and Fe in comparison with EHSP-2. The growth performance of N. salina suggests that EHSP-1 was more efficient than EHSP-2. The growth rate of N. salina in EHSP-1 was 1.07 times higher than the control whereas in EHSP-2 the growth rate was 0.58 times lower than the control. The maximum biomass concentration of N. salina was achieved in EHSP-1 and EHSP-2 were 0.37 and 0.21 g l-1 with a biomass productivity of 0.027 and 0.0152 g l-1 d-1 respectively. The results of biochemical analyses also suggest that protein, pigment and lipid yield of N. salina was positively stimulated by EHSP. The findings suggest that the best concentration of EHSP-1 and EHSP-2 to achieve maximum biomass and lipid production of the marine microalga N. salina were 8 and 4% respectively. EHSP-1 enhanced the biomass and lipid production without affecting the nutritional properties of N. salina suggesting its potential applicability in aquaculture, biofuel and other related industrial sectors.Keywords: Cellulase enzyme, Indigenous seaweed resources, Nannochloropsis salina, Nutrient rich media

Lipid production under a nutrient-sufficient condition outperforms starvation conditions due to a natural polarization of lipid content in algal biofilm

Attached algae cultivation for biofuel production has received proliferated attention given its advantage to reduce harvesting/dewatering costs and contamination risk. In this study, the effects of various nutrient starvation strategies on lipid production through the attached cultivation of Ettlia sp. YC001 was investigated. A detailed study on compositional variation over the depth of biofilms was followed to understand the phenomena within the biofilms under various nutrient conditions. As a result, the nutrient starvation strategy enhanced the lipid content of biofilms by 3–7 %, however, it limited biomass growth significantly. Ultimately, lipid production with sufficient nutrient supply outperformed those with nutrient starvations, reaching up to the maximum lipid productivity of 6.5 ± 0.1 g/m2/day. Compositional analyses over the depth of biofilms identified that high lipid accumulation was induced in the top layer of the biofilm regardless of medium condition as the top layers were naturally under stress from nutrient deficiency and high light exposure.

Maximizing Nitrogen Removal and Lipid Production by Microalgae under Mixotrophic Growth Using Response Surface Methodology: Towards Enhanced Biodiesel Production

The present study aimed to optimize synthetic wastewater composition as a mixotrophic medium for enhanced growth and lipid accumulation coupled with high nitrogen removal by the green microalga Chlorella sp. Individual effects of the three main independent variables (nitrate concentration, seawater ratio, and glycerol supplementation) were tested initially, then response surface methodology (RSM) was subsequently performed to explore the optimum combined conditions. The highest lipid productivity of 37.60 mg/L day was recorded at 25% seawater. Glycerol supplementation enhanced both lipid content and biomass production, which resulted in the highest recorded lipid productivity of 42.61 mg/L day at 4 g/L glycerol. Central composite design followed by numerical optimization was further applied which suggested NaNO3 concentration at 101.5 mg/L, seawater ration of 23.8%, and glycerol supplementation of 0.25 g/L as the optimum conditions for dual maximum lipid productivity and nitrogen removal of 46.9 mg/L day and 98.0%, respectively. Under the optimized conditions, dry weight and lipid content increased by 31.9% and 20.3%, respectively, over the control, which resulted in increase in lipid productivity by 71.5%. In addition, optimization process resulted in pronounced changes in fatty acid proportions where saturated fatty acids increased by 7.4% in the optimized culture with simultaneous reduction of polyunsaturated fatty acids. The estimated biodiesel characteristics calculated from the fatty acid methyl ester (FAMEs) profile showed agreement with the international standards, while optimized cultures showed an 8.5% lower degree of unsaturation, which resulted in higher cetane numbers and lower iodine values. This study provides economical approach for optimization and efficient nutrient recycling through cultivation of Chlorella sp. for further enhanced biodiesel production.

Enhancing biomass and lipid productivity of a green microalga Parachlorella kessleri for biodiesel production using rapid mutation of atmospheric and room temperature plasma

BackgroundMicroalgae, with their high adaptability to various stress conditions and rapid growth, are considered excellent biomass resources for lipid production and biodiesel feedstocks. However, lipid yield and productivity of the natural strains are common bottlenecks in their large-scale use for lipid production, which can be overcome by evolving new strains using conventional and advanced mutagenic techniques. It is challenging to generate microalgae strains capable of high lipid synthesis through natural selection. As a result, random mutagenesis is currently considered a viable option in many scenarios. The objective of this study was to explore atmospheric and room temperature plasma (ARTP) as a random mutagenesis technique to obtain high lipid-accumulating mutants of a green microalga for improved biodiesel production.ResultsA green microalgal species was isolated from the Chinese Yellow Sea and identified as Parachlorella kessleri (OM758328). The isolated microalga was subsequently mutated by ARTP to obtain high lipid-accumulating mutants. Based on the growth rate and lipid content, 5 mutants (named M1, M2, M4, M5, and M8) were selected from 15 pre-selected mutants. These five mutants varied in their growth rate from 0.33 to 0.68 day−1, with the lipid content varying between 0.25 g/L in M2 to 0.30 g/L in M8 at 10th day of cultivation. Among the mutants, M8 showed the maximum biomass productivity (0.046 g/L/day) and lipid productivity (20.19 mg/L/day), which were 75% and 44% higher than the wild strain, respectively. The triglyceride (TAG) content of M8 was found to be 0.56 g/L at 16th day of cultivation, which was 1.77-fold higher than that of the wild strain. Furthermore, M8 had the highest saturated fatty acids (C16-18) with the lowermost polyunsaturated fatty acid content, which are favorable properties of a biodiesel feedstock according to international standards.ConclusionThe mutant strain of P. kessleri developed by the ARTP technique exhibited significant improvements in biomass productivity, lipid content, and biodiesel quality. Therefore, the biomass of this mutant microalga could be a potential feedstock for biodiesel production.

Effects of sodium and magnesium supplement on lipid production and wastewater treatment by Rhodosporidium toruloides

Effects of sodium and magnesium supplement on biolipid production simultaneously with wastewater treatment by Rhodosporidium toruloides were investigated using synthetic wastewater with the composition similar to the mixture of real distillery and domestic wastewater. When Mg2+ was supplemented as MgCl2 at 200 mg/L, both lipid production and wastewater treatment were enhanced. The biomass and lipid production increased from 6.48 ± 0.69 and 0.96 ± 0.13 g/L to 7.78 ± 0.58 and 1.35 ± 0.02 g/L, respectively. The removal efficiencies for chemical oxygen demand (COD) and total phosphorus (TP) also increased from 72.09 ± 3.32 and 19.57 ± 2.51% to 79.20 ± 1.13 and 23.19 ± 3.07%, respectively. These increases were considered mainly due to the important role of Mg2+ in lipid synthesis, phosphate transfer, and carbohydrate metabolism. In comparison to Mg2+, the effect of Na+ depended on the supplement form. When 200 mg/L Na+ were provided as NaCl, maximum lipid production was 2.66 ± 0.11 g/L while only 1.98 ± 0.63 g/L when Na + provided as Na2SO4. For a better lipid production, the optimal concentrations of both Mg2+ and Na+ were considered around 200 mg/L. Both sodium and magnesium supplement did not show any obvious negative impact on biodiesel quality. The estimated values of important parameters of biodiesel with sodium or magnesium supplement met ASTM D6751 standard.

PH spurring microalgal cells to subsist onto palm kernel expeller for growing into biodiesel feedstock

The potentiality of microalgae as a feedstock for biodiesel production is actively being explored to resolve the inadequacy of biomass and lipid indexes conundrum, and economic infeasibility associated to the conventional cultivation system. Current study is an extension of a pre-optimized cultivation condition which has further elaborated the impact of pH on attached microalgal cultivation onto nutritional lignocellulosic waste; palm kernel expeller (PKE) by employing a novel periphytic growth and harvesting technique. The highest microalgal density was achieved at 10.9 ± 0.8 g/g-PKE in pH 5 cultivation medium with highest carbon-PKE assimilation. In fact, the microalgal growths under mixotrophic condition demonstrated a positive correlation between pH of cultivation medium and carbon-PKE assimilation by microalgae. The maximum lipid productivity was obtained at 33.1 ± 3.3 mg/L day from the attached microalgae of pH 11 medium. However, the lowest microalgal density was likewise attained at similar pH due to the trigger by which the carbon metabolic activity shifted towards lipid production instead of growth. Owing to the highest microalgal density attained at pH 5 medium, the gap of lipid productivities with pH 11 was narrowed down to merely 7.0 mg/L day. The attached microalgal feedstock harvested from this study was eventually found satiating most of the essential biodiesel properties in compliance with the international standards decreed by ASTM D6751-03 and EN 14214.

Inhibition of monogalactosyldiacylglycerol synthesis by down-regulation of MGD1 leads to membrane lipid remodeling and enhanced triacylglycerol biosynthesis in Chlamydomonas reinhardtii

BackgroundMembrane lipid remodeling involves regulating the physiochemical modification of cellular membranes against abiotic stress or senescence, and it could be a trigger to increase neutral lipid content. In algae and higher plants, monogalactosyldiacylglycerol (MGDG) constitutes the highest proportion of total membrane lipids and is highly reduced as part of the membrane lipid remodeling response under several abiotic stresses. However, genetic regulation of MGDG synthesis and its influence on lipid synthesis has not been studied in microalgae. For development of an industrial microalgae strain showing high accumulation of triacylglycerol (TAG) by promoting membrane lipid remodeling, MGDG synthase 1 (MGD1) down-regulated mutant of Chlamydomonas reinhardtii (Cr-mgd1) was generated and evaluated for its suitability for biodiesel feedstock.ResultsThe Cr-mgd1 showed a 65% decrease in CrMGD1 gene expression level, 22% reduction in MGDG content, and 1.39 and 5.40 times increase in diacylglyceryltrimethylhomoserines (DGTS) and TAG, respectively. The expression levels of most genes related to the decomposition of MGDG (plastid galactoglycerolipid degradation1) and TAG metabolism (diacylglycerol O-acyltransferase1, phospholipid:diacylglycerol acyltransferase, and major lipid droplet protein) were increased. The imbalance of DGDG/MGDG ratio in Cr-mgd1 caused reduced photosynthetic electron transport, resulting in less light energy utilization and increased reactive oxygen species levels. In addition, endoplasmic reticulum stress was induced by increased DGTS levels. Thus, accelerated TAG accumulation in Cr-mgd1 was stimulated by increased cellular stress as well as lipid remodeling. Under high light (HL) intensity (400 µmol photons/m2/s), TAG productivity in Cr-mgd1–HL (1.99 mg/L/d) was 2.71 times higher than that in wild type (WT–HL). Moreover, under both nitrogen starvation and high light intensity, the lipid (124.55 mg/L/d), TAG (20.03 mg/L/d), and maximum neutral lipid (56.13 mg/L/d) productivity were the highest.ConclusionsBy inducing lipid remodeling through the mgd1 gene expression regulation, the mutant not only showed high neutral lipid content but also reached the maximum neutral lipid productivity through cultivation under high light and nitrogen starvation conditions, thereby possessing improved biomass properties that are the most suitable for high quality biodiesel production. Thus, this mutant may help understand the role of MGD1 in lipid synthesis in Chlamydomonas and may be used to produce high amounts of TAG.

Simultaneous Treatment of Swine and Furfural Wastewater Integrated with Lipid Production of Chlorella pyrenoidosa

Adding organic compounds to wastewater can improve the carbon/nitrogen ratio and benefit microalgae growth. We studied microalgal growth, nutrient removal and lipid accumulation of Chlorella pyrenoidosa cultured in a mixture of swine wastewater (SW) and furfural wastewater (FW). The mix ratio of SW:DFW (diluted furfural wastewater) had a significant effect on microalgae growth. As the mix ratio of SW:DFW decreased from 1:0.5 to 1:19, the maximum microalgal biomass increased, while the specific growth rate initially increased and then decreased. The efficiency of nutrient removal also depended on the mix ratio of wastewater. The highest chemical oxygen demand (COD) removal efficiency (57.30%) occurred at the mix ratio of SW:DFW = 1:3. The highest removal efficiencies of total phosphorous (TP) reached 61.93% when the mix ratio of SW:DFW was 1:9. Wastewater at the mix ratio of SW:DFW = 1:19 had a maximum lipid productivity of 49.48 mg L−1 d−1, which was 4.9 times higher than that at a mix ratio of SW:DFW = 1:0.5. These results showed that C. pyrenoidosa can be used to remove nutrients from mixed wastewater sources and simultaneously produce algal lipids.

Carbon dioxide mitigation and biodiesel production by a marine microalga under mixotrophic mode by using transesterification by-product crude glycerol: A synergy of biofuels and waste valorization

The present work integrates carbon sequestration and waste reclamation with biofuel production into a single dynamic for encouraging eco-friendlier approaches ensuring environmental sustainability. To achieve improved carbon capturing and lipid production, a marine microalga Picochlorum soloecismus was selected. The maximum productivities of biomass and lipid were asserted to be 0.24 ± 0.02 gL−1d−1 and 58.2 ± 0.2 mgL−1d−1 under a CO2 supply of 17.0% at 0.7 vvm aeration in a 5 L photobioreactor under photoautotrophic condition. A low-priced mixotrophic medium was designed using CO2 with the transesterification by-product, i.e., crude glycerol. This produced maximum biomass and lipid productivities of 0.67 ± 0.04 and 0.13 ± 0.01 gL−1d−1 at a carbon fixation rate of 0.77 ± 0.06 gL−1d−1. The effect of mixotrophy was also investigated on a modified culture medium, i.e. Optimized ASN (Artificial Seawater Nutrient) prepared in our recent study generating a maximum lipid productivity of 0.31 ± 0.02 gL−1d−1at a carbon fixation rate of 0.80 ± 0.07 gL−1d−1. The use of crude glycerol in place of commercial glycerol for mixotrophy can reduce the medium cost by 22-fold. The methyl ester profile of biodiesel obtained under mixotrophy exhibited higher proportion of saturated fats and lower fraction of unsaturated fats. The fuel parameters lied within the established biodiesel standards.

Enhanced waste glycerol recycling by yeast for efficient biodiesel production: Towards waste biorefinery

The present study aimed to evaluate a new oleaginous yeast for biodiesel production with high potential of lipid accumulation in waste glycerol as a carbon source. Seven strains were isolated and identified using 5.8S-ITS based on their ability to assimilate glycerol. Naganishia diffluens CDU-M7rc showed the maximum lipid productivity (LP) of 881.9 mg L−1 d−1 at 96 h. Further optimization of pretreated waste glycerol (PWG) concentration enhanced the biomass yield to 20.3 g L−1 using 100 g L−1 PWG and enhanced lipid content to 34.36 dw% at 120 g L−1 PWG. However, the highest LP of 1.704 g L−1 d−1 was recorded at 100 g L−1 PWG, which represented 2.2-time more than the control. Using glucose as a carbon source, the dominant fatty acids in N. diffluens CDU-M7rc lipids were C16:0, C18:1, and C18:2, representing 23.91%, 55.45%, and 13.46% of total fatty acids, respectively. Utilization of PWG enhanced the proportion of C16:0 (33.39% of total fatty acids), with simultaneous reduction in C18:1 (41.12% of total fatty acids). Thus, supplementation of PWG enhanced saturated fatty acids proportion, which resulted in 10.8% reduction in the unsaturation degree of the produced biodiesel. All studied biodiesel characteristics showed acceptable values with the biodiesel international standards.

Screening of Lipid Production in Marine Cyanobacteria and Microalgae Grown in Ossein Effluent for Biodiesel Production

Microalgae and Cyanobacteria are potentially diverse, dominant photosynthetic organisms in nature. Initially, eight strains belonging to Marine cyanobacteria and Microalgae, based on growth, were selected. C. vulgaris BDU G91771 was used to study the possibility of utilizing ossein effluents. The organism was inoculated in two different effluents (HTDS and LTDS) with seawater and nutrient dilutions, namely (effluent, effluent with Seawater with N:P. The maximum lipid productivity was observed in 100%LTDS + Nutrients (Urea and superphosphate) with 16.8%. Lipid composition in fatty acids appeared to be suitable for biodiesel production. The results showed that the marine microalgae C. vulgaris BDU G91771 could be used to treat ossein effluents, and at the same time, to produce biodiesel sustainably.

Impact of polystyrene microplastics on major marine primary (phytoplankton) and secondary producers (copepod).

The effect of microplastic adsorption on marine microalgae Tetraselmis suecica, Amphora subtropica, and copepod Pseudodiaptomus annandalei was investigated in the present study. Fluorescence microscopic images were used to evaluate MP interactions with algae and copepods. T. suecica growth rate decreased with effects of 0.1µm polystyrene exposure to75 µl/100ml (0.899 to 0.601 abs), 50µl/100ml (0.996 to 0.632 abs) and 25µl/100ml (0.996 to 0.632 abs), respectively. On the other hand, at 10th day of experiment, the control T. suecica showed the highest growth rate (0.965 abs), chlorophyll concentration (Chl-'a' = 21.36µg/L; Chl-'b' = 13.65µg/L), and cell density (3.3 × 106 cells/ml). A marine diatom A. subtropica absorbed 2.0μm microplastics, and the maximal inhibition rate increased at higher MP concentration until 10th day. The highest MPs (75μl/100ml) treatment resulted in decreased growth rate of A. subtropica from 0.163 to 0.096 abs. A. subtropica (without MPs) had the highest lipid concentration of 27.15%, whereas T. suecica had the lowest lipid concentration of 11.2% (without MP). The maximum survival (80%) of P. annandalei was found in control on 15th day whereas on 12th day, the microplastics ingested copepod had the lowest survival rate (0%). On 15th day, the maximum Nauplii Production Rate (NPR) (19.33) female-1 was observed in control, whereas the minimum (17.33) female-1 NPR was observed in copepod ingested with MPs. The maximum lipid production (17.33% without MPs) was reported in control, whereas MPs fed copepods had the lowest lipid production (16%). Long-term exposure to polystyrene microplastics significantly reduced algae growth and chlorophyll concentration and also NPR and lipid concentration rate of copepod. We inferred that microplastic exposure of algae and copepods might results in persistent decreases in ingested carbon biomass over time.

Coupling of myo-inositol with salinity regulates ethylene-induced microalgal lipid hyperproduction in molasses wastewater

With the goal of cost-effective and high-efficient microalgae-based biodiesel production, this study evaluated the feasibility of the joint strategy concerning myo-inositol (MI) and salinity stress on lipid productivity of Monoraphidium sp. QLY-1 in molasses wastewater (MW). The maximal lipid productivity (147.79 mg L−1 d−1) was obtained under combined 0.5 g L−1 MI and 10 g L−1 NaCl treatment, which was 1.40-fold higher than the control. Meanwhile, the nutrients removal from MW was markedly increased under MI-NaCl treatment. Moreover, exogenous MI upregulated key lipogenic genes' expressions, activated autophagic activity and ethylene (ET) signaling, and ultimately alleviated the salinity-induced damage via reactive oxygen species (ROS) signaling. Further pharmacologic experiment confirmed the indispensable role of ET in the lipogenesis progress under the combined treatment. These data demonstrated the combined salinity stress and MI treatment to be capable for lipid hyperproduction and wastewater nutrients removal, which contributes to practically integrating the microalgae cultivation with wastewater treatment.

Raw Glycerol Based Medium for DHA and Lipids Production, Using the Marine Heterotrophic Microalga Crypthecodinium cohnii

Crude glycerol, a biodiesel industry byproduct, and corn steep liquor (CSL) derived from a starch industry, were used as carbon and nitrogen sources, respectively, for lipid production, using the heterotrophic microalga C. cohnii grown in a bench bioreactor, in a batch culture. The maximum biomass concentration, lipid content and lipid productivity attained were 5.34 g/L, 24.6% (w/w Dry Cell Weight-DCW) and 0.016 g L−1 h−1, respectively. Flow cytometry analysis was used to evaluate the impact of these substrates on the microalgae cells. A high proportion of intact cells with enzymatic (esterases) activity (>50%) was present throughout the cultivation time course. These results indicate that crude glycerol and CSL can be used in the medium formulation for DHA and lipid production using this microalga, which reduce the process costs in an expected maximum of 84%.

Research Article: Effect of different cobalt (CoCl2) concentrations on cell growth, some biochemical composition, and fatty acids profile of the marine microalga, Tetraselmis subcordiformis

The aim of this study was to determine the effects of cobalt concentration on cell growth, some biochemical composition, and fatty acids profile of the marine microalga Tetraselmis subcordiformis. Cobalt deprivations did not cause a considerable change in growth photosynthesis activity as compared to the control group. Induction of maximum lipid production was achieved using 0.001 mg L-1 of cobalt-deprived T. subcordiformis. The highest crude protein content (33.75 mg L-1) was observed in 0.001 mg L-1 cobalt. The highest and lowest lipid accumulation in T. subcordiformis was observed in 0.001 mg L-1 and 10 mg L-1 cobalt, respectively. Under cobalt deficient conditions, T. subcordiformis produced a large quantity of saturated fatty acids and the iodine and saponification value. Biodiesel characteristics were enhanced with Co+2 reduction. Also, biodiesel quality decreased with the increase of cobalt. The results showed that the maximum and minimum carotenoids were observed in 0.1 and 10 mg L-1 cobalt, respectively.

Isolation of a high-ammonium-tolerant Monoraphidium sp. and evaluation of its potential for biodiesel production

The economic challenges of microalgae biodiesel production, including the energy burden and water shortage, can be addressed simultaneously by using wastewater as a nitrogen source. However, as a major form of nitrogen, ammonium is toxic to most microalgae strains, which limits the use of ammonium-containing wastewater. High-ammonium-tolerant algal strains remain to be explored. In this study, a microalgal strain named HDMA-01, which was isolated from Lake Dongfeng in China, was selected using a high ammonium medium. Phylogenetic analysis suggested that HDMA-01 belongs to the genus Monoraphidium (Selenastraceae, Sphaeropleales), and both 18S ribosomal DNA and ITS sequences of HDMA-01 appeared to be new molecular records of the Monoraphidium species. HDMA-01 can multiply vigorously using acetic acid and ammonium in TAP medium, reaching a density of 2 ×107 mL−1 within 7 days. HDMA-01 showed strong tolerance for ammonium. At a high ammonium concentration of 14 mM, HDMA-01 achieved maximum biomass and lipid productivity of 78.9 mg L−1 day−1 and 13.8 mg L−1 day−1, which is the highest among other Monoraphidium strains under similar cultivation conditions. Together with its ideal fatty acid profile, HDMA-01 has great potential for development as a promising strain used in biodiesel feedstock and high-ammonium tolerance biotechnology.

Insights into lipid accumulation features of Coccomyxa sp. IITRSTKM4 under nutrient limitation regimes

Microalgal lipids are deemed to be the most promising alternative to petroleum fuels, enduring the pressure of fuel scarcity. Screening oleaginous microalgae from natural habitats are imperative, as novel strains producing enhanced biofuel components can make them economically viable. The present investigation involves the isolation and characterization of a novel microalga Coccomyxa sp. IITRSTKM4, under nitrogen (N)-, phosphorus (P)-, and sulfur (S)- limitation The reduction in biomass and chlorophyll content of nutrient-starved cells was compensated with stable PSII efficiency and enhanced cellular lipid content. The maximum lipid content ( ∼ 41 %) and lipid productivity (22 ± 2.2 mg/L/d) were achieved under N-deficiency and synergistic NPS-limitation, respectively. However, S-deficient cells resulted in increased carbohydrate content ( ∼ 33%). Further, analysis of biochemical components suggested that protein pools were diverted towards the synthesis of storage molecules (lipid/carbohydrate), aiding cell survival under nutrient starvation. FAME profiling of obtained lipid indicated that it majorly contains C16–C18 fatty acids. The estimated biodiesel quality index parameters have complied with the American (ASTM D6751) and European (EN 14214) standards, thus establishing Coccomyxa sp. IITRSTKM4 a suitable candidate for biodiesel production. Moreover, the production of lipid and carbohydrate under N- and S-deficiency evidences the versatility of the strain for producing biofuels. • Novel oleaginous microalgal strain isolated from water of Ganga Ghat, Haridwar. • Lipid accumulation under different nutrient regimes was investigated. • N/P deficiency improved lipid, whereas S-deficiency increased carbohydrate content. • Maximum lipid productivity was achieved in synergistic N/P/S-limitation. • Biodiesel properties complied with international fuel standards.

Overexpression of fatty acid synthesis genes in Synechocystis sp. PCC 6803 with disrupted glycogen synthesis increases lipid production with further enhancement under copper induced oxidative stress

In the present study, fatty acid synthesis genes such as alpha and beta subunits of acetyl CoA carboxylase (accA and accD) were overexpressed in the glgC (Glucose-1-phosphate adenylyltransferase) knockout Synechocystis sp. PCC 6803. The biomass and lipid contents were evaluated in both the wild type and the engineered strains after copper treatment. The maximum lipid production of 0.981 g/L with the productivity of 81.75 mg/L/d was obtained from the copper treated ΔglgC + A-OX strain, which showed a 3.3-fold increase compared to the untreated wild type with satisfactory biodiesel properties. After copper treatment the knockout strain improved the unsaturated fatty acids level contributing to the increase of the saturated and mono-unsaturated ratio with improvement of the fuel quality. Copper induced oxidative stress also improved the photosynthetic pigments in engineered strains leading to increased tolerance against oxidative stress in the engineered strains. The copper treatment increased the antioxidant enzyme activities in the engineered strains especially in ΔglgC + A-OX strain. The carbon flux to lipid synthesis was enhanced by the engineered strains particularly with the knockout-overexpression strains. The Synechocystis sp. PCC 6803 engineered with ΔglgC + A-OX showed high potential for fuel production after the copper treatment.

Influence of Light Conditions on Microalgae Growth and Content of Lipids, Carotenoids, and Fatty Acid Composition.

Simple SummaryMicroalgae are a valuable natural resource for a variety of value-added products. This determines the relevance of developments aimed at increasing the efficiency of their cultivation. First of all, the growth of microalgae is determined by the impact of light. The main parameters characterizing the light conditions during the cultivation of microalgae are light intensity, duration of lighting, and the use of rays of different spectral composition. Manipulations with the duration of the photoperiod and the use of pulsed light can avoid photodamage of microalgae cells and create conditions for the most efficient absorption of light photons. The optimal light conditions for photosynthesis, growth, accumulation of lipids, fatty acid composition, and carotenes content differ both in different taxonomic groups of microalgae and in different strains of the same species.Microalgae are a valuable natural resource for a variety of value-added products. The growth of microalgae is determined by the impact of many factors, but, from the point of view of the implementation of autotrophic growth, light is of primary importance. This work presents an overview of the influence of light conditions on the growth of microalgae, the content of lipids, carotenoids, and the composition of fatty acids in their biomass, taking into account parameters such as the intensity, duration of lighting, and use of rays of different spectral composition. The optimal light intensity for the growth of microalgae lies in the following range: 26−400 µmol photons m−2 s−1. An increase in light intensity leads to an activation of lipid synthesis. For maximum lipid productivity, various microalgae species and strains need lighting of different intensities: from 60 to 700 µmol photons m−2 s−1. Strong light preferentially increases the triacylglyceride content. The intensity of lighting has a regulating effect on the synthesis of fatty acids, carotenoids, including β-carotene, lutein and astaxanthin. In intense lighting conditions, saturated fatty acids usually accumulate, as well as monounsaturated ones, and the number of polyunsaturated fatty acids decreases. Red as well as blue LED lighting improves the biomass productivity of microalgae of various taxonomic groups. Changing the duration of the photoperiod, the use of pulsed light can stimulate microalgae growth, the production of lipids, and carotenoids. The simultaneous use of light and other stresses contributes to a stronger effect on the productivity of algae.

SCREENING OF FUNGI FOR PRODUCTION AND PURIFICATION OF OMEGA-3 FATTYACID

Omega fatty acids, major importance in the prevention or treatment of a range of human diseases or disorders related with inflammation. These fatty acids are found in transgenic plants, fungi, and animals and even in microorganisms but in major amounts can be extracted from fatty fish. However, due to bioaccumulation of fat-soluble vitamins and high levels of saturated and omega-6 fatty acids, they may have deleterious health effects. It becomes necessary to search for novel and rich sources containing omega-3 fatty acids and one of the alternatives include fungi. The present study deals with production and purification of omega-3 fatty acids from Trichoderma viride and Aspergillus niger. In the present study, the main objective was to explore the beneficial effects of fungi for the maximum lipid production through optimized conditions and the results clearly showed that Trichoderma viride was the significantly highest lipid producer, with lipid production at initial pH 6.0 and incubation temperature 40℃.