Increased Lipid Production Research Articles

Elevated CO2 improves both lipid accumulation and growth rate in the glucose-6-phosphate dehydrogenase engineered Phaeodactylum tricornutum

BackgroundNumerous studies have shown that stress induction and genetic engineering can effectively increase lipid accumulation, but lead to a decrease of growth in the majority of microalgae. We previously found that elevated CO2 concentration increased lipid productivity as well as growth in Phaeodactylum tricornutum, along with an enhancement of the oxidative pentose phosphate pathway (OPPP) activity. The purpose of this work directed toward the verification of the critical role of glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme in the OPPP, in lipid accumulation in P. tricornutum and its simultaneous rapid growth rate under high-CO2 (0.15%) cultivation.ResultsIn this study, G6PDH was identified as a target for algal strain improvement, wherein G6PDH gene was successfully overexpressed and antisense knockdown in P. tricornutum, and systematic comparisons of the photosynthesis performance, algal growth, lipid content, fatty acid profiles, NADPH production, G6PDH activity and transcriptional abundance were performed. The results showed that, due to the enhanced G6PDH activity, transcriptional abundance and NAPDH production, overexpression of G6PDH accompanied by high-CO2 cultivation resulted in a much higher of both lipid content and growth in P. tricornutum, while knockdown of G6PDH greatly decreased algal growth as well as lipid accumulation. In addition, the total proportions of saturated and unsaturated fatty acid, especially the polyunsaturated fatty acid eicosapentaenoic acid (EPA; C20:5, n-3), were highly increased in high-CO2 cultivated G6PDH overexpressed strains.ConclusionsThe successful of overexpression and antisense knockdown of G6PDH well demonstrated the positive influence of G6PDH on algal growth and lipid accumulation in P. tricornutum. The improvement of algal growth, lipid content as well as polyunsaturated fatty acids in high-CO2 cultivated G6PDH overexpressed P. tricornutum suggested this G6PDH overexpression-high CO2 cultivation pattern provides an efficient and economical route for algal strain improvement to develop algal-based biodiesel production.

SIMULTANEOUS LIPID AND CAROTENOID PRODUCTION BY STEPWISE FED-BATCH CULTIVATION OF Rhodotorula mucilaginosa WITH CRUDE GLYCEROL

Abstract In the present study, an innovative cultivation strategy of Rhodotorula mucilaginosa CCT 7688 to accumulate both lipids and high added value carotenoids was proposed, with the potential to contribute to the economic feasibility of microbial oils in comparison with vegetable oils. The stepwise fed-batch cultivation with crude glycerol feeding at 24 h, 96 h, and 144 h, with the addition of magnesium to the initial culture medium, resulted in a lipid content of 51.0 ± 0.3 % CDW, biomass concentration of 21.00 ± 0.48 g L-1, total lipid production of 10.72 ± 0.18 g L-1, lipid productivity of 0.037 ± 0.001 g L-1 h-1, volumetric carotenoid production of 2843.2 ± 282.0 μg L-1, and carotenoid productivity of 9.87 ± 0.98 μg L-1 h-1. These values represent a 6-fold increase in lipid content, a 19-fold increase in lipid production, and a 2-fold increase in carotenoid production compared to batch cultivation.

A two-stage model with nitrogen and silicon limitation enhances lipid productivity and biodiesel features of the marine bloom-forming diatom Skeletonema costatum

To enhance biodiesel production and quality from a bloom-forming diatom Skeletonema costatum, a two-stage model, in which cells were cultured in nutrient replete conditions first and then transferred to nutrient limitation conditions, was explored. Compared to one-stage model, nutrient limitation in the second stage significantly increased lipid content in spite of decreasing growth; consequently, Si-limitation and N-Si-limitation respectively increased lipid productivity by 37.6% and 76.7% for 6 h induction, and 42.8% and 113.7% for 12 induction. Nutrient limitation enhanced the proportions of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) but reduced polyunsaturated fatty acid (PUFA). Therefore, N-Si-limitation reduced iodine value by 33.7% and 45.6% but increased cetane number by 6.4% and 21.6% for 6 and 24 h induction, respectively. These findings indicate that the two-stage model with N-Si-limitation can enhance lipid productivity as well as biodiesel quality from diatoms.

FAX2 Mediates Fatty Acid Export from Plastids in Developing Arabidopsis Seeds.

Vegetable oils are mainly stored in the form of triacylglycerol (TAG) in oilseeds. Fatty acids (FAs), one of the building blocks for TAG assembly, are synthesized in plastids and then exported to the endoplasmic reticulum for storage oil synthesis. A recent study demonstrated that the export of FAs from plastids was mediated by a FAX (FA export) family protein. However, the significance of FAs export from plastid during seed oil accumulation has not been investigated. In this study, we found that FAX2 was highly expressed in developing Arabidopsis seeds and the expression level was consistent with FAs synthesis activity. FAX2 mutant seeds showed an approximately 18% reduction of lipid levels compared with wild-type seeds. By contrast, overexpression of FAX2 enhanced seed lipid accumulation by up to 30%. The FAs export activity of FAX2 was confirmed by yeast mutant cell complementation analysis. Our results showed that FAX2 could interact with other proteins to facilitate FAs transport. Taken together, these results indicate that FAX2-mediated FA export from plastids is important for seed oil accumulation, and that FAX2 can be used as a target gene for increasing lipid production in oilseeds.

Metabolic traits specific for lipid-overproducing strain of Mucor circinelloides WJ11 identified by genome-scale modeling approach.

The genome-scale metabolic model of a lipid-overproducing strain of Mucor circinelloides WJ11 was developed. The model (iNI1159) contained 1,159 genes, 648 EC numbers, 1,537 metabolites, and 1,355 metabolic reactions, which were localized in different compartments of the cell. Using flux balance analysis (FBA), the iNI1159 model was validated by predicting the specific growth rate. The metabolic traits investigated by phenotypic phase plane analysis (PhPP) showed a relationship between the nutrient uptake rate, cell growth, and the triacylglycerol production rate, demonstrating the strength of the model. A putative set of metabolic reactions affecting the lipid-accumulation process was identified when the metabolic flux distributions under nitrogen-limited conditions were altered by performing fast flux variability analysis (fastFVA) and relative flux change. Comparative analysis of the metabolic models of the lipid-overproducing strain WJ11 (iNI1159) and the reference strain CBS277.49 (iWV1213) using both fastFVA and coordinate hit-and-run with rounding (CHRR) showed that the flux distributions between these two models were significantly different. Notably, a higher flux distribution through lipid metabolisms such as lanosterol, zymosterol, glycerolipid and fatty acids biosynthesis in iNI1159 was observed, leading to an increased lipid production when compared to iWV1213. In contrast, iWV1213 exhibited a higher flux distribution across carbohydrate and amino acid metabolisms and thus generated a high flux for biomass production. This study demonstrated that iNI1159 is an effective predictive tool for the pathway engineering of oleaginous strains for the production of diversified oleochemicals with industrial relevance.

Engineering Trichosporon oleaginosus for enhanced production of lipid from volatile fatty acids as carbon source

Trichosporon oleaginosus is one of the most promising hosts for microbial lipid production owing to its high-productivity; In an effort to develop an economical production process, we engineered T. oleaginosus towards high-lipid production from volatile fatty acids (VFA) derived from anaerobic fermentation of food waste. First, we established a method for labeling intracellular lipid with lipophilic BODIPY fluorescent dye. Next, a random library was constructed by treatment with a chemical mutagen, and high-lipid producers were screened using fluorescence-activated cell sorting. Subsequently, one clone, N14, was successfully isolated, which exhibited 3-fold higher lipid production (19.4%) in VFA (6 g/L) media than the wild-type strain, and also showed increased lipid production in higher concentrations of VFA (18 or 24 g/L). Based on fatty acid methyl ester (FAME) analysis, N14 contained higher stearic acid (C18:0) and oleic acid (C18:1) content compared with those of the wild-type strain.

Overexpression of malic enzyme isoform 2 in Chlamydomonas reinhardtii PTS42 increases lipid production

Genetic modification of microalgae has been performing to overcome the economic and technical difficulties associated with biodiesel production. In this study, to explore a new approach to exploiting a metabolic pathway for effective lipid production, we engineered Chlamydomonas reinhardtii PTS42 to overexpress malic enzyme isoform 2 (ME2) which catalyzes the conversion of malate to pyruvate. Overexpression of ME2 resulted in increase of mRNA level (around 2–3 fold) and increase of the pyruvate content (42.4% and 44.8% respectively) in transgenic M16 and M17, respectively. The fatty acid content and the lipid content of M17 were increased by 23.4 and 19.9% respectively compared to parental lines under the nitrogen deprivation condition. However, no significant changes in fatty acids composition was observed in transgenic lines. These results demonstrate that ME2 overexpression enhances the availability of pyruvate for fatty acid biosynthesis and lipid production in C. reinhardtii.

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.

Using fluazifop‐p‐butyl for low cost increases in lipid accumulation for the generation of algal biofuels from Chlorella vulgaris

The demand for sustainable, low‐emission fuels is increasing with the global expansion of industrialization. Biofuels have the potential to meet this need without the problematic addition of carbon into the earth's atmosphere. Algae, a potential biofuels feedstock, have the capability to quickly accumulate biomass under various conditions, including low‐nutritional growth medium and a reduced need for arable land. Current research is seeking to increase organismal efficiency in order to increase economic feasibility. Previous work has shown that exposing algae to environmental stressors or limitations, such as nitrogen deprivation, can increase lipid production in the cultures, though this is typically accompanied by a decrease in overall biomass. Nitrogen deprivation is also expensive to facilitate, so finding more economical methods is paramount to increasing algal biofuel feasibility. In this study, Chlorella vulgaris, a unicellular green alga, was exposed to a formulation of an inexpensive and readily available mass‐produced herbicide that targets acetyl Co‐A carboxylase with its active ingredient, fluazifop‐p‐butyl. The compositional changes of the algae cultures were monitored as well as the photosynthetic efficiency. Preliminary results have shown an increase in percent lipids in cultures exposed to the herbicide formulation, though the overall biomass decreased. Current results in this study will be presented.Support or Funding InformationThis research was made possible by NASA West Virginia Space Grant Consortium, Training Grant # NNX15AI01HThis material is based upon work supported by the National Science Foundation under Cooperative Agreement No. OIA‐1458952This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Understanding the functions of endogenous DOF transcript factor in Chlamydomonas reinhardtii

BackgroundThe regulation of genes related to lipid metabolism by genetic engineering is an important way to increase the accumulation of lipids in microalgae. DNA binding with one finger (DOF) is a plant-specific transcription factor in higher plants, where it regulates carbon and nitrogen metabolic pathways by regulating key genes involved in these pathways. Overexpression of DOF can increase lipid production in plants; however, it is not clear whether overexpression of DOF can increase lipids in microalgae.ResultsIn this study, we cloned a DOF transcription factor, crDOF, from Chlamydomonas reinhardtii. The sequence of this transcription factor is 1875 bp and encodes a peptide of 624 amino acids with a conserved DOF domain. Overexpression of crDOF in C. reinhardtii significantly increased the intracellular lipid content. The content of total fatty acids in the transgenic algae line Tranc-crDOF-12 was 126.01 μg/mg (dry weight), which was 23.24% higher than that of the wild type. Additionally, the content of unsaturated fatty acids in the transgenic Tranc-crDOF-12 line increased significantly. Fluorescence quantitative PCR analysis showed that in the transgenic line Tranc-crDOF-12, the expression levels of BCC1, FAT1, SQD1, MGD1, DGD1 and PGP1 genes were significantly upregulated, while the expression levels of ACP1, ACS1, CIS1 and SQD2 were downregulated.ConclusionsOur results confirm that crDOF increases intracellular lipids in C. reinhardtii by regulating key genes involved in lipid metabolism. According to these findings, we propose that enhancing the lipid content in microalgae by overexpressing DOF may be achieved in other industrial strains of microalgae and be employed for the industrial production of biodiesel.

Global warming and oligotrophication lead to increased lipid production in marine phytoplankton

Earth temperature is rising and oligotrophication is becoming apparent even in coastal seas. In this changing environment, phytoplankton use carbon and nutrients to form important biomolecules, including lipids. However, the link between lipid production and changing environment is still unexplored. Therefore, we investigated the phytoplankton lipid production in the diatom Chaetoceros pseudocurvisetus cultures under controlled temperatures ranging from 10 to 30 °C and nutrient regimes mimicking oligotrophic and eutrophic conditions. Results were compared to plankton community's lipid production in the northern Adriatic at two stations considered as oligotrophic and mesotrophic during an annual monthly sampling. In order to gain detailed information on the investigated system, we supplemented lipid data with chlorophyll a concentrations, phytoplankton taxonomy, cell abundances and nutrient concentration along with hydrographic parameters. We found enhanced particulate lipid production at higher temperatures, and substantially higher lipid production in oligotrophic conditions. Enhanced lipid production has two opposing roles in carbon sequestration; it can act as a retainer or a sinker. Lipid remodeling, including change in ratio of phospholipids and glycolipids, is more affected by the nutrient status, than the temperature increase. Triacylglycerol accumulation was observed under the nitrogen starvation.

Characterization of Fatty Acid EXporters involved in fatty acid transport for oil accumulation in the green alga Chlamydomonas reinhardtii

BackgroundIn the past few decades, microalgae biofuel has become one of the most interesting sources of renewable energy. However, the higher cost of microalgae biofuel compared to that of petroleum prevented microalgae biofuel production. Therefore, the research on increasing lipid productivity from microalgae becomes more important. The lipid production source, triacylglycerol biosynthesis in microalgae requires short chain fatty acids as substrates, which are synthesized in chloroplasts. However, the transport mechanism of fatty acids from microalgae chloroplasts to cytosol remains unknown.ResultscDNAs from two homologs of the Arabidopsis fatty acid exporter 1 (FAX1) were cloned from Chlamydomonas reinhardtii and were named crfax1 and crfax2. Both CrFAXs were involved in fatty acid transport, and their substrates were mainly C16 and C18 fatty acids. Overexpression of both CrFAXs increased the accumulation of the total lipid content in algae cells, and the fatty acid compositions were changed under normal TAP or nitrogen deprivation conditions. Overexpression of both CrFAXs also increased the chlorophyll content. The MGDG content was decreased but the TAG, DAG, DGDG and other lipid contents were increased in CrFAXs overexpression strains.ConclusionThese results reveal that CrFAX1 and CrFAX2 were involved in mediating fatty acid export for lipids biosynthesis in C. reinhardtii. In addition, overexpression of both CrFAXs obviously increased the intracellular lipid content, especially the triacylglycerol content in microalgae, which provides a potential technology for the production of more biofuels using microalgae.

Improved lipid production via fatty acid biosynthesis and free fatty acid recycling in engineered Synechocystis sp. PCC 6803

BackgroundCyanobacteria are potential sources for third generation biofuels. Their capacity for biofuel production has been widely improved using metabolically engineered strains. In this study, we employed metabolic engineering design with target genes involved in selected processes including the fatty acid synthesis (a cassette of accD, accA, accC and accB encoding acetyl-CoA carboxylase, ACC), phospholipid hydrolysis (lipA encoding lipase A), alkane synthesis (aar encoding acyl-ACP reductase, AAR), and recycling of free fatty acid (FFA) (aas encoding acyl–acyl carrier protein synthetase, AAS) in the unicellular cyanobacterium Synechocystis sp. PCC 6803.ResultsTo enhance lipid production, engineered strains were successfully obtained including an aas-overexpressing strain (OXAas), an aas-overexpressing strain with aar knockout (OXAas/KOAar), and an accDACB-overexpressing strain with lipA knockout (OXAccDACB/KOLipA). All engineered strains grew slightly slower than wild-type (WT), as well as with reduced levels of intracellular pigment levels of chlorophyll a and carotenoids. A higher lipid content was noted in all the engineered strains compared to WT cells, especially in OXAas, with maximal content and production rate of 34.5% w/DCW and 41.4 mg/L/day, respectively, during growth phase at day 4. The OXAccDACB/KOLipA strain, with an impediment of phospholipid hydrolysis to FFA, also showed a similarly high content of total lipid of about 32.5% w/DCW but a lower production rate of 31.5 mg/L/day due to a reduced cell growth. The knockout interruptions generated, upon a downstream flow from intermediate fatty acyl-ACP, an induced unsaturated lipid production as observed in OXAas/KOAar and OXAccDACB/KOLipA strains with 5.4% and 3.1% w/DCW, respectively.ConclusionsAmong the three metabolically engineered Synechocystis strains, the OXAas with enhanced free fatty acid recycling had the highest efficiency to increase lipid production.

Increasing lipid production using an NADP+-dependent malic enzyme from Rhodococcus jostii.

The occurrence of NADP+-dependent malic enzymes (NADP+-MEs) in several Rhodococcus strains was analysed. The NADP+-ME number in Rhodococcus genomes seemed to be a strain-dependent property. Total NADP+-ME activity increased by 1.8- and 2.6-fold in the oleaginous Rhodococcus jostii RHA1 and Rhodococcus opacus PD630 strains during cultivation under nitrogen-limiting conditions. Total NADP+-ME activity inhibition by sesamol resulted in a significant decrease of the cellular biomass and lipid production in oleaginous rhodococci. A non-redundant ME coded by the RHA1_RS44255 gene located in a megaplasmid (pRHL3) of R. jostii RHA1 was characterized and its heterologous expression in Escherichia coli resulted in a twofold increase in ME activity in an NADP+-dependent manner. The overexpression of RHA1_RS44255 in RHA1 and PD630 strains grown on glucose promoted an increase in total NADP+-ME activity and an up to 1.9-foldincrease in total fatty acid production without sacrificing cellular biomass. On the other hand, its expression in Rhodococcus fascians F7 grown on glycerol resulted in a 1.3-1.4-foldincrease in total fatty acid content. The results of this study confirmed the contribution of NADP+-MEs to TAG accumulation in oleaginous rhodococci and the utility of these enzymes as an alternative approach to increase bacterial oil production from different carbon sources.

Delta-9 fatty acid desaturase overexpression enhanced lipid production and oleic acid content in Rhodosporidium toruloides for preferable yeast lipid production

The oil plants provide a sufficient source of renewable lipid production for alternative fuel and chemical supplies as an alternative to the depleting fossil source, but the environmental effect from these plants' cropping is a concern. The high oleic acid (OA; C18:1) content in plant-derived products provide advantages of multiple uses with improved oxidative stability and a wide range of applicable temperature. Here we used a promising lipid producer, the oleaginous yeast Rhodosporidium toruloides, to attempt to obtain an OA-enriched lipid. Saccharomyces cerevisiae OLE1 (ScOLE1) gene encodes Δ9 fatty acid desaturase (Δ9FAD), which is generally known to synthesize palmitoleic acid (POA; C16:1) and OA, but the functions of putative R.toruloides Δ9FAD gene are not well understood. In a complementary test, the RtΔ9FAD gene rescued the survival of an OA-deficient Scole1Δ mutant, and we introduced the RtΔ9FAD gene into R.toruloides strains for the production of OA-enriched lipid. Increasing lipid production was observed in ScOLE1 and genomic RtΔ9FAD gene-overexpressing R.toruloides strains. The ScOLE1 transformant output fivefold more OA content in total amount, with >70% of total lipid. Different enhancing effects from the protein coding sequence and genomic sequence of RtΔ9FAD genes were also observed. Overall, this study resulted in ScOLE1 and RtΔ9FAD gene overexpression in R.toruloides to obtain OA-enriched lipid as a candidate source of designed biodiesel and lipid-related chemicals.

Targeted knockout of phospholipase A2 to increase lipid productivity in Chlamydomonas reinhardtii for biodiesel production

Biofuel derived from microalgae have several advantages over other oleaginous crops, however, still needs to be improved with its cost aspect and can be achieved by developing of a strain with improved lipid productivity. In this study, the CRISPR-Cas9 system was incorporated to carry out a target-specific knockout of the phospholipase A2 gene in Chlamydomonas reinhardtii. The targeted gene encodes a key enzyme in the Lands cycle. As a result, the mutants showed a characteristic of increased diacylglycerol pool, followed by a higher accumulation of triacylglycerol without being significantly compensated with the cell growth. As a result, the overall lipid productivities of phospholipase A2 knockout mutants have increased by up to 64.25% (to 80.92 g L−1 d−1). This study can provide crucial information for the biodiesel industry.

Combination Effect of Temperature and Light Intensity on Lipid Productivity of Tetradesmus obliquus

Lipid enhancement is important to reduce production cost thus increasing the commercial values of microalgal biofuel production. Physical stress such as temperature and light intensity are known to increase lipid productivity because these factors might affect the phase transition of lipid, macromolecule formation and physiochemical reactions of microalgae. In this study, the effect of light intensity and temperature on lipid productivity of Tetradesmus obliquus was studied. T.obliquus UPSI-JRM02 was cultured in BG11 media at different temperature range (25–40°C) and light intensity (4000–30000 lux), respectively, within 14 days of growth period. The highest lipid productivity was obtained at temperature and light intensity of 36°C and 23500 lux. At this condition, 27 mg/L/day of lipid productivity and 23% of total lipid was successfully produced. The result shows the possibility of increasing T.obliquus lipid productivity by giving physical stress to the cell.

Evaluation of transcription profile of acetyl-CoA carboxylase (ACCase) and acyl-ACP synthetase (AAS) to reveal their roles in induced lipid accumulation of Synechococcus sp. HS01

Abstract It was earlier shown that the mixotrophic cultivation of Synechococcus sp. HS01 in ostrich oil-containing BG11 medium leads to an up to 2.82- fold increase in lipid productivity compared with autotrophic condition. A follow-up investigation was carried out to divulge whether conditions that would increase the lipid content in Synechococcus sp. HS01, bringing about constantly more pool towards the main route for fatty acids synthesis. To this end, the expression patterns of two genes including acc as the main enzyme involved in fatty acid synthesis pathway, converting Acetyl-CoA to Malonyl-CoA and aas gene which convert free fatty acids to active Acyl carrier protein (ACP) (through esterification) were carefully analyzed under different culture conditions. While there is a direct association between the expression of acc gene and changes in lipid content of glucose and acetate-grown cultures, no direct relationship exists between the expression of this gene in ostrich oil-grown culture and nitrogen-deficient conditions. Reduced acc gene expression and increased expression of aas gene in conjunction with increased lipid contents in ostrich oil-grown cultures indicated that exogenous fatty acids can be applied directly to the intracellular lipid synthesis and a possible strategy for achieving greater amount of lipids produced by cyanobacteria.

Synergistic effect of co-culture of microalga and actinomycete in diluted chicken manure digestate for lipid production

Microalgae have high potential as organisms that can be used for biodiesel production because they can accumulate high amounts of lipids in a similar manner to oleaginous plants. However, the economic feasibility of their lipid production is still in question. Possible methods of improving that feasibility involve a reduction in cultivation costs using effluents along with an increase in lipid production by co-cultivation with plant growth-supporting microorganisms. Previous studies have found that actinomycetes possess a potential as plant growth-promoters. Thus, this research study is aimed at investigating the effects of the co-cultivation of actinomycetes with microalgae on growth and lipid production in diluted chicken manure digestate. In this study, over 190 actinomycetes were screened for their ability to grow in the digestate, as well as for their plant growth promoting abilities. The actinomycete, Nocardia bhagyanarayanae I-27, could promote chlorophyll a, biomass and lipid contents in a co-culture with green microalga Tetradesmus obliquus AARL G022 in 25% diluted digestate. Microalgal major fatty acid methyl esters are a suitable substrate for biodiesel production. In addition, the essential Ω3 fatty acids, including α-linolenic acid and eicosapentaenoic acid, also increased in volume. Thus, the co-cultivation of plant growth promoting actinomycetes with microalgae in wastewater could be an alternative strategy used to increase biomass and lipid production.

Synthesis and characterization of fluorescent dyes and their applications for the enhancement of growth rate of Chlorella vulgaris

Spectral conversion of solar radiation from green to red light can enhance the photosynthesis efficiency of microalgae. This can lead to significant increase in microalgal growth. Four perylene-based fluorescent dyes were synthesized to convert wavelengths of light from green (500–570 nm) to orange-red (580–650 nm). These dyes were applied in microalgal cultivation system using two methodologies: (1) light-converting layer, and (2) light-converting medium. The dyes were dissolved in either ethanol or water to form light-converting layers between microalgae culture and the light source. Under converted light in both set-ups, Chlorella vulgaris cultures showed maximum increase in lipid productivity by 13.00% and 17.15%, and biomass productivity by 31.65% and 37.66% compared to the control. Overall, the cultivation results confirmed beneficial effects of modified light on microalgae cultures both on their lipid and biomass productivities. Note that both growth parameters achieved higher performance in the light-converting medium thereby the effectiveness of the cultivation method was validated.