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[Display omitted] • Optimization of microalgae culture through a two-stage cultivation strategy. • Biomass accumulation was enhanced by 23.62% under optimal conditions. • Optimal dual stress enhanced lipid and SFA content by 128.38% and 56.30%. • Microalgae recycling efficiency increased under dual stress environments. In this study, a two-stage culture strategy was refined to concurrently enhance the growth and lipid accumulation of Tetradesmus obliquus. The results unveiled that, during the initial stage, the optimal conditions for biomass accumulation were achieved with 0.02 mg·L−1 Cu2+ concentration and red light. Under these conditions, biomass accumulation reached 0.628 g·L−1, marking a substantial 23.62 % increase compared to the control group. In the second stage, the optimal conditions for lipid accumulation were identified as 0.5 mg·L−1 Cu2+ concentration and red light, achieving 64.25 mg·g−1·d−1 and marking a 128.38 % increase over the control. Furthermore, the fatty acid analysis results revealed an 18.85 % increase in the saturated fatty acid content, indicating enhanced combustion performance of microalgae cultivated under the dual stress of red light and 0.5 mg·L−1 Cu2+. This study offers insights into the potential application of Tetradesmus obliquus in biofuel production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multifactor regulation improved the biomass and lipids in Chlamydomonas reinhardtii. • The optimal cultivation conditions were 30 °C, 150 μE/m2/s, and 24/0h photoperiod. • The maximal biomass and lipid content in C. reinhardtii reached 1.92 g/L and 41.10 %. • Lipid productivity was promoted by 3.01 times under optimized culture conditions. • The biodiesel properties were enhanced by altering temperature and light regimes. This study investigated the impacts of various culture temperatures and light regimes on growth and biochemical constituents of Chlamydomonas reinhardtii under carbon-supply and nitrogen-limited conditions to improve oil production in algal cells. Results displayed that under a 30 ℃ and 150 μE/m2/s regime, there was a significant increase in biomass, total lipids, and lipid productivity. Specifically, these parameters reached 1.83 g/L, 36.25 %, and 130.73 mg/L/d, respectively. Remarkably, prolonging the photoperiod further enhanced the aforementioned three parameters, reaching peak levels of 1.92 g/L, 41.10 %, and 157.54 mg/L/d, respectively, recorded at a 24/0h photoperiod. Compared with cultures grown under normal conditions, these values displayed increments of 1.21-fold, 74.88 %, and 3.01-fold, respectively. Additionally, under optimal conditions, the soluble sugar content reached 79.72 mg/g, and the biodiesel properties were improved. These findings indicate that moderately increasing temperature, light intensity, and photoperiod could achieve the co-production of biomass, lipids, and sugars in C. reinhardtii. [ABSTRACT FROM AUTHOR]

[Display omitted] • C. sorokiniana showed superior tolerance capacity on high acetate dosage up to 30 g/L. • Heterotrophy benefits to algal growth and lipogenesis when supplying 20 g/L acetate. • Inhibition of photosynthesis led to poor mixotrophic growth under 20 g/L acetate. • Heterotrophy produced superior amino acid profiling and more linoleic acid (50%). • Heterotrophic repeat fed-batch mode resulted in 23.4 g/L biomass and 7.0 g/L lipid. The low-cost carbon source, acetate, was utilized to feed a linoleic acid-rich Chlorella sorokiniana for microalgal biomass and lipid accumulation. Remarkably high tolerance capability to high acetate dosage up to 30 g/L was observed, with heterotrophy being the preferred trophic mode for algal growth and lipogenesis when supplemented 20 g/L acetate. Transcriptome analysis revealed a marked activation of pathways involved in acetate bioconversion and lipogenesis upon exposure to high-level of acetate. However, the enhancement of photorespiration inhibited photosynthesis, which ultimately led to a decrease in biomass and lipid under mixotrophy. Heterotrophic acetate-feeding generated more superior amino acid profiling of algal biomass and a predominant linoleic acid content (50 %). Heterotrophic repeat fed-batch strategy in 5 L fermenter significantly increased the growth performance and lipid titer, with the highest levels achieved being 23.4 g/L and 7.0 g/L, respectively. This work provides a viable approach for bio-products production through acetate-based heterotrophic algal cultivation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fed-batch fermentation achieved the highest lipid and biomass reported in Mucor. • The biochemical profile of fed-batch fermentation obtained products was examined. • The expression levels of key genes involved in lipid synthesis had up-regulated. • Numerous abiotic factors thrived during the optimization of fed-batch cultivation. This study aimed to improve the lipid and biomass yields of Mucor circinelloides WJ11 by implementing four different fed-batch fermentation strategies, varied in time and glucose concentration (S1-S4). The S1 fermentation strategy yielded the highest biomass, lipid, and fatty acid content (22 ± 0.7 g/L, 53 ± 1.2 %, and 28 ± 1.6 %) after 120 and 144 h, respectively. The γ-linolenic acid titer of 0.75 ± 0.0 g/L was greatest in S3 after 48 h. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to analyze the transcription of key genes involved in lipid accumulation. The glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and ATP-citrate lyase genes showed increased expression levels. Fourier-transform infrared (FTIR) spectroscopy was used to analyze the biochemical profile during fermentation strategies. Optimal abiotic factors for production efficiency included pH 6.5, 25–26 °C, 15 % (v/v) inoculum, 500 rpm, 20 %-30 % dissolved oxygen, and 120 h fermentation. Glucose co-feeding offers valuable insights to develop effective fermentation strategies for lipid production. [ABSTRACT FROM AUTHOR]

[Display omitted] • ARTP-ethanol co-mutation for synchronous enhancement of lipid and astaxanthin. • Improved key enzyme activity, gene expression for lipid and astaxanthin biosynthesis. • Elucidated mechanisms of lipid and astaxanthin accumulation by ARTP and ethanol. • Upregulation of genes nubpl , Abcc 2, PAO related to lipid and astaxanthin accumulation. Haematococcus lacustris is a precious algal species renowned for its ability to simultaneous production of astaxanthin and lipid. However, its slow growth rate necessitates the development of appropriate mutagenesis methodologies to effectively enhance its synchronous production of both astaxanthin and lipid. This study introduced the co-mutation of Atmospheric and Room Temperature Plasma (ARTP) and ethanol. The performance and preliminary mechanisms underlying the combined accumulation of astaxanthin and lipid in H. lacustris under both mutations by ARTP and ethanol were comparatively analyzed. Combined astaxanthin and lipid contents relative to total cell mass in the 110–2 strain reached 54.4%, surpassing that of strain 0–3 and the control by 17.0% and 47.6% respectively. Transcriptome level analysis revealed how both ethanol and ARTP induction promote the expressions of carotenoid and lipid synthesis genes and related enzymatic activities. Upregulation of genes associated with cell activity contributed to lipid and astaxanthin metabolism in multi pathways. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oleaginous yeast grown on solid lipid-rich side stream Cocoa Fatty Acid Distillate. • Adaptive Laboratory Evolution (ALE) enhanced growth and single cell oil production. • ALE improved biomass by >2-fold and lipid content by 3- to 4-fold. • Transcriptomics reveal potential mechanism which improve growth and lipid content. • Oleaginous yeast strains generated with high amounts of saturated lipid content. Single cell oil production using oleaginous yeasts is a promising alternative to animal and plant-derived lipids. But substrate costs for microbial fermentation are a major bottleneck. Using side streams as alternative to substrates like glucose, for growing yeast, is a potential cost-effective solution. By combining a previously reported process of growing yeasts on a solid cocoa fatty acid distillate side stream with adaptive evolution techniques, the growth of oleaginous yeast Yarrowia lipolytica was improved by 2-fold. The lipid titre was also boosted by more than 3-fold. Using transcriptomics, key genes were identified that are possibly involved in tailoring of lipid composition, side stream utilisation and enhancement of lipid titres. Candidate genes were also identified that might enable efficient growth and utilization of fatty acids and triacylglycerides found in cocoa fatty acid distillate. In summary, this research has improved the understanding of side stream utilisation for lipid production in oleaginous yeast. [ABSTRACT FROM AUTHOR]

• Nutrient enrichment enhanced the biomass and lipid productivity in C. gracilis. • Protein, carbohydrate and lipid content was highest in 2 f setup of T. weissflogii. • Nutrient limitation enhanced phenol and flavonoid content in T. weissflogii. Marine diatoms have high adaptability and are known to accumulate lipids under nutrient stress conditions. The present study involves determining the effect of varying macro and micronutrients on growth kinetics and metabolite production of oleaginous marine diatoms, Thalassiosira weissflogii and Chaetoceros gracilis. The results highlighted that C. gracilis and T. weissflogii showed maximum biomass yield of 0.86 ± 0.06 g/L and 0.76 ± 0.01 g/L in the 2 f and f supplemented medium respectively. A 2.5-fold increase in cellular lipid content was recorded in the 2 f culture setup of both strains ranging from 20 % to 26.7 % (w/w). The study also reveals that high eutrophic nutrient media (f , 2 f and 4 f) triggered biomass productivity as well as total protein and carbohydrate content in both strains. Thus, providing a reproducible insight of trophic flexibility of diatoms, concomitant with the increment in multiple commercially valuable products. [ABSTRACT FROM AUTHOR]

Mechanism of enhanced microalgal biomass and lipid accumulation through symbiosis between a highly succinic acid-producing strain of Escherichia coli SUC and Aurantiochytrium sp. SW1. [Display omitted] • E. coli SUC was screened to establish a symbiotic system with SW1. • E. coli SUC promoted the growth of SW1 by dual regulation mechanism. • Under optimized conditions, SW1 achieved biomass of 27.83 g/L and lipids of 4.87 g/L. Microalgae, known for rapid growth and lipid richness, hold potential in biofuels and high-value biomolecules. The symbiotic link with bacteria is crucial in large-scale open cultures. This study explores algal-bacterial interactions using a symbiotic model, evaluating acid-resistant Lactic acid bacteria (LAB), stress-resilient Bacillus subtilis and Bacillus licheniformis , and various Escherichia coli strains in the Aurantiochytrium sp. SW1 system. It was observed that E. coli SUC significantly enhanced the growth and lipid production of Aurantiochytrium sp. SW1 by increasing enzyme activity (NAD-IDH, NAD-ME, G6PDH) while maintaining sustained succinic acid release. Optimal co-culture conditions included temperature 28 °C, a 1:10 algae-to-bacteria ratio, and pH 8. Under these conditions, Aurantiochytrium sp. SW1 biomass increased 3.17-fold to 27.83 g/L, and total lipid content increased 2.63-fold to 4.87 g/L. These findings have implications for more efficient microalgal lipid production and large-scale cultivation. [ABSTRACT FROM AUTHOR]

[Display omitted] • S stress induced rapid accumulation of lipids in T. minus up to 54% of DW. • High concentration of SO 4 2− markedly increased the N uptake and biomass of T. minus. • Two-step culture is an effective method to promote lipid and POA production. • The lipid content of T. minus was negatively correlated with the cellular S content. Tribonema minus , a promising filamentous oleaginous microalga, was cultured under different nutrient concentrations and different culture modes (fed-batch culture, two-step culture) to study the method of rapid regulation of its lipid metabolism. In contrast to many other oleaginous microalgae, T. minus did not show that nitrogen stress promoted lipid accumulation; however, sulfur deficiency promoted rapid lipid accumulation with a maximum lipid content of 54% of dry weight. Increasing the MgSO 4 concentration significantly increased nitrogen uptake and biomass (10.09 g/L). Lipid productivity was significantly increased by the two-step culture using a medium with a high concentration of MgSO 4 in the first step and a sulfur-free medium in the second step. In addition, it was found that the lipid content of T. minus was negatively correlated with the intracellular sulfur content when the intracellular sulfur content was below 0.6%. This study provides a new approach for industrial lipid production in T. minus. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel self-flocculating blue-green microalga Limnothrix sp. was isolated. • High self-flocculating efficiency (>90 %) was obtained in municipal wastewater. • It showed both excellent growth and lipid production performance. • Self-flocculation is related to extracellular proteins, calcium and magnesium ions. • Blue light induced algal aggregation due to extracellular polysaccharides secretion. The present study evaluated the growth, self-flocculation, lipid content, and pollutants removal by Limnothrix sp. BASMWW-9 isolated from municipal wastewater treatment system and cultivated in municipal wastewater. The biomass yield and lipid content after 6 days of cultivation were 1.07 g dw/L and 27.34 %dw, respectively. In addition, its self-flocculating ability reached up to 90 % after harvesting time of 180 min. Moreover, COD, NH 3 -N, TN, and TP removal efficiencies were 71.65 %, 81.89 %, 74.64 %, and 80.16 %, respectively. The self-flocculation performance of Limnothrix sp. was greatly associated to its morphology and production of extracellular polymeric substances (EPS), with significant positive impact of the high calcium and magnesium content in municipal wastewater. Interestingly, blue light irradiation during harvest enhanced the aggregation and floc formation as a floating biomat, which was attributed to enhanced polysaccharides production. This study provides innovative harvest method for Limnothrix sp. BASMWW-9 cultivated in wastewater using blue light for enhanced lipid recovery. [ABSTRACT FROM AUTHOR]

• Deep-learning-based image recognition was developed for lipid quantification of yeast culture. • The trained model detected cell and lipid droplets with high accuracy. • The trained model monitored lipid droplets in real-time using simple light microscopic images. • The image-based lipid quantification showed high accuracy comparable to GC–MS. Intracellular lipid droplets (LDs), subcellular organelles playing a role in long-term carbon storage, have immense potential in biofuel and dietary lipid production. Monitoring the state of LDs in living cells is of utmost importance for quick biomass harvest and screening promising isolates. Here, a deep-learning-based segmentation model was developed for automatic detection and segmentation of LDs using the model yeast species Lipomyces starkeyi , leading to fast and accurate quantification of lipid contents in liquid cultures. The trained model detected the yeast's cell and LDs in light microscopic images with an accuracy of 98% and 92%, respectively. Lipid content prediction using pixel numbers counted in segmented LDs showed high similarity to lipid quantification results obtained with gas chromatography-mass spectrometry. This automated quantification can highly reduce cost and time in real-time monitoring of lipid production, thereby providing an efficient tool in bio-fermentation. [ABSTRACT FROM AUTHOR]

• Seven common herbal extraction residues (HERs) were compared for lipid production. • Radix paeoniae alba residue (RPAR) was superior for sugar and lipid production. • Reuse of pretreatment liquor (PL) for RPAR pretreatment obtained 241.6 g/L sugars. • Fed-batch culture of the PL as feeding medium led to high lipid production. • Micro-biodiesel prepared from the HERs showed high-quality fuel properties. Valorization of herbal extraction residues (HERs) into value-added products is pivotal for the sustainability of Chinese medicine industry. Here, seven different enzymatic hydrolysates of dilute acid pretreated HERs were evaluated for lipid production by Cutaneotrichosporon oleaginosum. Among them, the highest sugar yield via hydrolysis and the maximum lipid production were obtained from Radix paeoniae alba residue (RPAR). More interestingly, high proportion of sugar polymers was disintegrated into fermentable sugars during the pretreatment step, allowing a cheap non-enzymatic route for producing sugars from RPAR. A repeated dilute acid pretreatment gained a high sugar concentration of 241.6 g/L through reusing the pretreatment liquor (PL) for four times. Biomass, lipid concentration, and lipid content achieved 49.5 g/L, 35.7 g/L and 72.2 %, respectively, using fed-batch culture of PL. The biodiesel parameters indicated lipids produced from HERs were suitable for biodiesel production. This study offers a cost-effective way to upgrade the HERs waste into micro-biodiesel. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-stage fermentation process proposed for efficient bioconversion. • Engineered Y. lipolytica could convert syngas into β-carotene and lipids. • Tolerance up to 20 g/L acetic acid seen in the yeast strain. • Optimal lipid and β-carotene production were found at pH 6.0 in bioreactors. • The dominant lipid identified was C18:1, which is suited for biodiesel production. An engineered Yarrowia lipolytica strain was successfully employed to produce β-carotene and lipids from acetic acid, a product of syngas fermentation by Clostridium aceticum. The strain showed acetic acid tolerance up to concentrations of 20 g/L. Flask experiments yielded a peak lipid content of 33.7 % and β-carotene concentration of 13.6 mg/g under specific nutrient conditions. The study also investigated pH effects on production in bioreactors, revealing optimal lipid and β-carotene contents at pH 6.0, reaching 22.9 % and 44 mg/g, respectively. Lipid profiles were consistent across experiments, with C18:1 being the dominant compound at approximately 50 %. This research underscores a green revolution in bioprocessing, showing how biocatalysts can convert syngas, a potentially polluting byproduct, into valuable β-carotene and lipids with a Y. lipolytica strain. [ABSTRACT FROM AUTHOR]

[Display omitted] • C.curvatus concurrently assimilated GlcNAc and glucose for lipid production. • GlcNAc has the capacity to supply both carbon and nitrogen sources. • The co-fermentation of rice hydrolysates and chitin hydrolysate was effective. • Scaling-up experiments in a 5-L bioreactor resulted in lipid content of 60.1 %. • The fatty acid compositions of lipids were similar to that for vegetable oils. Microbial lipids were produced through a two-stage process with Cryptococcus curvatus by co-fermenting rice and shrimp shells hydrolysates. In the first stage, biomass production of glucose and N -acetylglucosamine was optimized by response surface methodology with the maximum biomass yield (17.60 g/L) under optimum conditions (43.2 g/L mixed sugar concentration, pH 5.8, 200 rpm, and 28 °C). In the second stage, according to a single-factor optimization setting (43.2 g/L sugar mixture solutions, pH 5.5, and shift time of 36 h), lipid titer of 10.08 g/L with content of 55.30 % was achieved. Scaling up to a 5-L bioreactor increased lipid content to 60.07 % with 0.233 g/g yield. When Cryptococcus curvatus was cultured in the blends of rice hydrolysates and shrimp shells hydrolysate, lipid content and yield were 52.25 % and 0.204 g/g. The fatty acid compositions of lipid were similar to those of typical vegetable oils. [ABSTRACT FROM AUTHOR]

[Display omitted] • Citricoccus sp. P2 degraded 44.63% of lignin and produced 23.96% of lipid content. • Citricoccus sp. P2 has demonstrated high effectiveness in LDCs conversion. • Genome sequencing revealed a biological funneling pathway for LDCs into lipid. • Lipid yield was 0.39 g/g LMS-treated lignin. • Non-sterilized fermentation efficiently improved lipid production from LDCs. Lignin-derived compounds (LDCs) bioconversion into lipids is a promising yet challenging task. This study focuses on the isolation of the ligninolytic bacterium Citricoccus sp. P2 and investigates its mechanism for producing lipids from LDCs. Although strain P2 exhibits a relatively low lignin degradation rate of 44.63%, it efficiently degrades various concentrations of LDCs. The highest degradation rate is observed when incubated with 0.6 g/L vanillic acid, 0.6 g/L syringic acid, 0.8 g/L p-coumaric acid, and 0.4 g/L phenol, resulting in respective lipid yields of 0.16 g/L, 0.13 g/L, 0.24 g/L, and 0.13 g/L. The genome of strain P2 provides insights into LDCs bioconversion into lipids and stress tolerance. Moreover, Citricoccus sp. P2 has been successfully developed a non-sterilized lipid production using its native alkali-halophilic characteristics, which significantly enhances the lipid yield. This study presents a promising platform for lipids production from LDCs and has potential to promote valorization of lignin. [ABSTRACT FROM AUTHOR]

[Display omitted] • 20 K-lux light/3x-nutrients exhibited max. astaxanthin 54.4 mg/L by C. zofingiensis. • 4–8 K-lux successive light increase and 5% CO 2 exhibited the best biomass yield. • The maximum lipid 37% accumulation was obtained at 5% CO 2 and 20 k-lux light. • 20 K-lux light/3x-nutrients exhibited max. astaxanthin content 16.7 mg/g DCW. • Two-stage designed bioprocess boosts astaxanthin yield of C. zofingiensis. Microalgal astaxanthin possesses numerous bioactivities and has several health applications. The current research focuses on designing and optimizing the two-stage mixotrophic bioprocess by Chlorella zofingiensis for astaxanthin production. Gradual increase in light intensity (4-8k-lux) and 3x micronutrient concentration were the key parameters for maximizing biomass yield of 2.5 g/L during 15 days of stage I. Furthermore, stress conditions (excessive CO 2, light, salinity, etc.) enhanced astaxanthin yield at stage II. 20k lux light, 3x nutrients, and 5% CO 2 were the best ranges for maximum astaxanthin production. Maximum biomass yield and astaxanthin content were 3.3 g/L and 16.7 mg/g, respectively, after 29 days of bioprocess. Astaxanthin biosynthesis was also affected by salinity, but less than other parameters. Astaxanthin bioprocess resulted in enhanced lipid yields of 35–37%, which could be used for biodiesel. This study shows promising scale-up potential with attractive sustainability features of Chlorella zofingiensis model for commercial astaxanthin-lipid biorefinery. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3x-nutrients resulted in maximum lutein 71.13 mg/L from Chlorella sorokiniana C16. • 10 k lux light exhibited the best microalgae growth, biomass, and lutein yields. • The maximum 27% lipid accumulation was obtained at 75% salinity. • 32 °C temperature was determined for the maximum lutein content 17.4 mg/g DCW. • Two-stage optimized bioprocess boosts lutein production with minimal biomass loss. The current work aims to isolate high lutein-producing microalgae and maximize lutein production under a sustainable lutein-lipid biorefinery scheme. Lutein reduces retinitis, macular degeneration risk and improves eye health. An effective bioprocess design optimized nutrients, temperature, light, and salinity for biomass and lutein yield enhancement. 3X macro/micronutrients maximally enhanced biomass and lutein yields, 5.2 g/Land 71.13 mg/L. Temperature 32 °C exhibited maximum 17.4 mg/g lutein content and 10 k lux was most favorable for growth and lutein yield (15.47 mg/g). A 25% seawater addition led maximum of 21–27% lipid that could be used for biodiesel. Isolate was identified as Chlorella sorokiniana C16, which exhibited one of the highest lutein yields reported among recent studies, positioning it as a promising candidate for commercial lutein production. This study provides valuable insights into an effective bioprocess design and highlights the C16 strain potential as a sustainable platform for high-value lutein production under a biorefinery scheme. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • EA-TPP was firstly developed to extract lipids of wet Nannochloropsis biomass. • Cellulase was the best suitable enzyme to disrupt Nannochloropsis biomass. • EA-TPP achieved lipid extraction yield of 88.7% under optimal conditions. • EA-TPP was a green and efficient approach to extract microalgae lipids. Abstract A green and efficient enzyme assisted three phase partitioning (EA-TPP) process was firstly developed to extract microalgal lipids using wet Nannochloropsis sp. biomass. In the pretreatment of microalgal biomass by four hydrolytic enzymes, TPP obtained a higher TFAs lipid extraction efficiency by cellulase compared with the resting enzymes. After optimization by EA-TPP of the wet disrupted Nannochloropsis biomass (3 g), the maximum TFAs extraction yield (90.40%) was attained at 20% ammonium sulphate, 6–7 pH, 1:2 slurry/ tert -butanol ratio and 70 °C for 2 h incubation time and two extraction cycles. Moreover, results also revealed that the lipidic species compositions of Nannochloropsis sp. biomass were greatly related with the EA-TPP parameters. In the laboratory scale for wet disrupted microalgae biomass, EA-TPP process achieved 88.70% TFAs extraction yield under the optimized conditions. In all, EA-TPP process could be a promising approach to extract microalgae lipids for food application using wet microalgae biomass. [ABSTRACT FROM AUTHOR]

Highlights • The uncertain effects from free ammonia on algal lipids are investigated. • A moderate concentration of free ammonia promoted lipid content in algal cells. • The percentage of unsaturated fatty acids increased under alkaline condition. Abstract Anaerobic wastewater potentially was an ideal medium for cultivating microalgae. The coupled effect of ammonium, temperature and pH on lipids accumulation was a core issue during algal culture using anaerobic wastewater. Therefore, their combined effects on Chlorella pyrenoidosa culture and lipids accumulation in anaerobic effluent were investigated. Free ammonia induced from the rising pH and temperature inhibited algal growth, but significantly promoted lipid accumulation. The highest lipids content reached 30.2% when pH rose to 8.3–8.5 (25 °C, ammonium 280 mg/L), which was 1.6-fold higher than that under neutral condition. Moreover, the percentage of unsaturated fatty acids (un-SFAs) increased to 74.8–77.9% at pH 8.3–8.5, whereas it was only 56.1–58.9% under neutral condition. The C18:2 and C18:3 dominated the un-SFAs increase at high pH, typically the percentage of C18:3 increased by 74.5–153.1%. This study provides a potential way for lipid accumulation in algal culture using anaerobic wastewater. [ABSTRACT FROM AUTHOR]

• Bioremediation with flue gas CO 2 utilization potential of Chlorella was tested. • Wastewater cocktail based biodiesel and lutein production in open raceway ponds. • 100% nitrogenous substance with 85–91% carbon-phosphorus remediation were obtained. • Biomass and lutein productivity of 6.21 ± 0.16, 1.2 ± 0.08 g m−2 day−1 was achieved. • Two-fold increase in lipid content and 80.74 ± 0.07 mg L−1 day−1 CO 2 was utilized. We evaluated wastewater remediation and CO 2 utilization potential of Chlorella minutissima from flue gas in a raceway pond, while synthesizing lutein and lipid for potential healthcare and biofuel application. A mix of 20% kitchen waste, 10 g L−1 of poultry litter waste and 5% flue gas was maintained while cultivating the microalga. Complete removal of nitrate, nitrite and ammonium, 85% carbon and 91% phosphorus was observed. An average areal biomass productivity of 4.06 ± 0.12 g m−2 day−1 with a specific growth rate of 0.34 ± 0.03 day−1 was observed within 9 days. Biomass productivity of 6.21 ± 0.16 g m−2 day−1 with a specific growth rate of 0.34 ± 0.03 day−1 was achieved during winter. Furthermore, lipid content with appropriate fatty acid composition 1.04:1 (saturation:unsaturation) increased from 25% to 58%. Additionally, lutein productivity of 1.2 ± 0.08 mgL−1 day−1, while utilizing 80.74 ± 0.07 mg L−1 day−1 of CO 2 from 5% flue gas was obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] • SCP and lipid were coproduced from wheat straw and (NH 4) 2 SO 4 by oleaginous yeast. • Engineered Trichosporon cutaneum MP11 with excellent adaptability was employed. • The cellulosic SCP and lipid titer reached 24.4 ± 1.5 g/L and 11.8 ± 1.2 g/L at 48 h. • Residual (NH 4) 2 SO 4 in wastewater was recycled with stable fermentation performance. Co-production of single cell protein (SCP) and lipid from lignocellulose-derived carbohydrates and inorganic ammonia offers a promising alternative for poultry or aquaculture feeds. An engineered oleaginous yeast Trichosporon cutaneum MP11 showed great potential for producing SCP and lipid from wheat straw and ammonia sulfate with minimum nutrient input. Trichosporon cutaneum MP11 showed stronger SCP and lipid fermentability using dry acid pretreated and biodetoxified wheat straw than using pure sugars. The residual ammonium sulfate in fermentation broth was recycled up to five times, resulting in ∼70% of nitrogen fixation into SCP. The overall yield of SCP and lipid from lignocellulose-derived sugars was 0.15 g/g and 0.11 g/g, respectively. This translates to the production of one ton of SCP (0.56 ton) and lipid (0.44 ton) from 6.6 tons of wheat straw, or one ton of SCP and lipid containing yeast cells (dry) from 4.8 tons of wheat straw. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chaperone and CRISPRi were first applied in algae under thermophilic condition. • Transcriptional result depicts temperature and CRISPRi effects on algal metabolism. • PGi strain showed 2.56 g/L, 23.5 and 893 mg/L of biomass, lutein and lipid at 35°C. • Thermophilic conditions affect the biomass, lipid, and CO 2 uptake in microalgae. • PGi strain had 1.08 g-CO 2 /g-DCW of CO 2 assimilation ability in mixotrophic culture. Microalgae are widely recognized as a promising bioresource for producing renewable fuels and chemicals. Microalgal biorefinery has tremendous potential for incorporation into circular bioeconomy, including sustainability, cascading use, and waste reduction. In this study, genetic engineering was used to enhance the growth, lipid and lutein productivity of Chlamydomonas reinhardtii including strains of CC400, PY9, pCHS, and PG. Notably, CRISPRi mediated on phosphoenolpyruvate carboxylase (PEPC 1) gene to down-regulate the branch pathway from glycolysis to partitioning more carbon flux to lipid was explored under meso -thermophilic condition. The best chassis PGi, which has overexpressed chaperone GroELS and applied CRISPRi resulting in the highest biomass of 2.56 g/L and also boosted the lipids and lutein with 893 and 23.5 mg/L, respectively at 35°C. Finally, all strains with CRISPRi exhibited higher transcriptional levels of the crucial genes from photosynthesis, starch, lipid and lutein metabolism, thus reaching a CO 2 assimilation of 1.087 g-CO 2 /g-DCW in mixotrophic condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnesium aminoclay (MgA) induces CO 2 absorption and oxidative stress. • The effect of MgA on growth and lipid accumulation is Chlorella strain-dependent. • MgA improved the total lipid content and hexane extractability of Chlorella KR-1. • MgA promoted triacylglycerol biosynthesis but reduced cell wall thickness. Magnesium aminoclay nanoparticles (MgANs) exert opposing effects on photosynthetic microalgae by promoting carbon dioxide (CO 2) uptake and inducing oxidative stress. This study explored the potential application of MgAN in the production of algal lipids under high CO 2 concentrations. The impact of MgAN (0.05–1.0 g/L) on cell growth, lipid accumulation, and solvent extractability varied among three tested oleaginous Chlorella strains (N113, KR-1, and M082). Among them, only KR-1 exhibited significant improvement in both total lipid content (379.4 mg/g cell) and hexane lipid extraction efficiency (54.5%) in the presence of MgAN compared to those of controls (320.3 mg/g cell and 46.1%, respectively). This improvement was attributed to the increased biosynthesis of triacylglycerols and a thinner cell wall based on thin-layer chromatography and electronic microscopy, respectively. These findings suggest that using MgAN with robust algal strains can enhance the efficiency of cost-intensive extraction processes while simultaneously increasing the algal lipid content. [ABSTRACT FROM AUTHOR]

Highlights • A mixotrophic microalgae Chlorella sp. G-9 was separated from a WWTP. • Increasing TOC/TN ratio of wastewater promoted algal growth and nutrient removal. • Growth rate of microalgae did not increase as TOC/TN ratio increased from 24 to 30. • 99.58% and 99.61% nitrogen was removed in the wastewaters with TOC/TN of 24 and 30. • The highest lipid content of 36.5% was achieved in wastewater with TOC/TN of 30. Abstract This study investigated the biomass/lipid production, nutrient removal and fatty acid composition of an isolated mixotrophic microalga (Chlorella sp. G-9) cultured in simulated wastewater with different TOC/TN ratio. As the TOC/TN ratio of wastewater increased from 0 to 24, the growth rate of Chlorella sp. G-9 increased gradually, but did not increase further at 30. Nutrient removal was related to microalgae growth. In the wastewater with TOC/TN ratio of 24 and 30, 99.58% and 99.61% nitrogen was removed, respectively. In conditions of initial TOC/TN ratios of 24 and 30, Chlorella sp. G-9 could accumulate lipid as high as 35.3% and 36.5%, respectively. The corresponding lipid productivities were 34.2 and 32.6 mg L−1 d−1, respectively, which were 13.7 and 13.0 times higher than those in photoautotrophic condition. Increasing the initial TOC/TN ratio of the wastewater could slightly increase the saturated degree in fatty acid, thereby improving the stability of biodiesel. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Oleaginous microalga Scenedesmus sp. was immobilized in alginate gel beads. • Two-phase purify assembly of biogas upgrading and phytoremediation was effective. • Immobilized microalgae biomass with high lipids and pigments were obtained. • Microalgal lipids are composed of C16-C18 (>98%) with estimated high cetane number. Abstract Oleaginous microalga Scenedesmus sp. was immobilized in alginate-gel beads and applied as two-phase purify unit for biogas and anaerobic digester effluent from palm oil mill. Optimal microalgal cell concentration and bead volume ratio were 106 cells mL−1 and 25% v/v, respectively. The use of 20% effluent and light intensity at 128 µmol·proton·m−2 s−1 most promoted CO 2 removal by immobilized microalgae and achieved the maximum CO 2 removal rate of 4.63 kg-CO 2 day−1 m−3. This process upgraded methane content in biogas (>95%) and completely remove nitrogen and phosphorus in the effluent. After process operation, 2.98 g L−1 microalgal biomass with 35.92% lipid content were recovered by simple sieving method. Microalgal lipids are composed of C16-C18 (>98%) with prospect high cetane number and short ignition delay time. This study has shown the promising biorefinery concept which is effective not only in CO 2 fixation, biogas upgrading and pollutant removal but also cost-effective production of microalgae-based biofuel. [ABSTRACT FROM AUTHOR]

Highlights • Temperature was the most influential factor on sugar production from algal biomass. • HCl resulted in higher monosaccharide recovery than NaOH. • No effect of enzymatic hydrolysis operational factors on sugar production was found. • High carbohydrate solubilisations were achieved from biomasses grown in wastewater. • Biomass grown in synthetic medium achieved the highest monosaccharide recovery. Abstract Biomass grown in wastewater treatment photobioreactors is a cheap raw material with high contents of carbohydrates, proteins and lipids. This work studies the production of fermentable monosaccharides from three biomasses grown in piggery wastewater (P), domestic wastewater (W) and synthetic medium (S) by applying chemical pretreatment and enzymatic hydrolysis, using a Taguchi design. ANOVA identified temperature, chemical reagent type and chemical reagent concentration as significant operational parameters. However, the biomass concentration, pretreatment time, enzyme dosage and enzymatic hydrolysis time had no remarkable effect. The bacterial content of the biomass had no relevant impact on carbohydrate and protein solubilisation but had a remarkable effect on the degradation of the released carbohydrates (57, 60 and 37% for P, W and S), while also affecting lipid solubilisation. Pretreatment with HCl 2 M at 120 °C resulted the optimal conditions, achieving a monosaccharide recovery of 53, 59 and 80% for P, W and S biomasses, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MAAs production was higher in UV-B range than in the UV-A range. • UV-B exposer accountable for saturation of lipid which result in good fuel quality. • UV protectant and algal lipid can be recovered in sequential extraction. • Nitrogen abundance and high oxidative stress is helpful in synthesis of UV protectant. • UVA is good for food properties and UVB are good for fuel property of cyanobacteria. Abstract With objective to design cyanobacterial biorefinery, taking Lyngbya as a model organism, a detail sequential protocol has been developed for production of UV protectant and lipids. This study addresses ultra violet radiations (UVR), exposure time of UVRT, nitrogen stress, salinity, oxidative stress to produce UV protectant and lipid in cyanobacteria. To evaluate these parameters a design of experiment (DOE; using a 2 k design) was performed. Based on chemical solubility property of UV protectant in form of mycosporine like amino acid (MAAs) and lipids were extracted. Quantitative and qualitative assay of UV protectant was confirmed by spectrophotometric scanning and Fourier-transform infrared spectroscopy and lipid through fatty acid methyl esters analysis. Nitrogen abundance and high oxidative stress is helpful in the synthesis of UV protectant. This study concluded, UV exposure is good strategy to induce synthesis of UV protectant and saturated lipid productivity. This biorefinery approach encourages economical and environmentally sustainable options. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A SM-PBR was constructed for nutrients recovery from LL and lipids production. • The membrane module can protect microalgae cells from LL contamination. • Excess phosphate feeding increased lipid content but decreased biomass production. • N recovery and lipids production were boosted in the SM-PBR than traditional PBR. Abstract The aim of this work was to realize high-efficiency nutrients recovery from landfill leachate (LL) for microalgal lipids production. Negative effects of LL on microalgal lipid synthesis was revealed and a scalable membrane-based tubular photobioreactor (SM-PBR) was proposed to offset these negative effects. Microalgal biomass concentration was improved from 0 g/L in the traditional PBR to 2.13 g/L in the SM-PBR. Major operating conditions were optimized to enhance nutrients recovery and lipid productivity. The maximum N recovery efficiency of 74.31% and the maximum daily lipid production of 404.98 mg/d were obtained under the volume ratio of 5:3 (microalgae culture/LL stream) and phosphate feeding concentration of 50 mg/L. The obtained lipid was convinced to have a good combustion and anti-degradation property, with high cetane number (>52%) and low linolenic acid content (<12%). The SM-PBR provided a feasible approach for large-scale microalgal lipid production with LL. [ABSTRACT FROM AUTHOR]

Highlights • Protein recovery by pH-shift from a consortium microalgae-bacteria biomass. • ANOVA of NaOH concentration, temperature and time effect on process parameters. • Intermediate alkaline concentration (0.5 M NaOH) provided maxima extraction yields. • High solubilisation by alkaline hydrolysis but low acidic precipitation efficiency. • Co-extraction of lipids increased with process intensity. Abstract The influence of three variables on key parameters of the protein extraction process (an alkaline hydrolysis followed by an acidic precipitation) for biomass from innovative photo-bioreactors for pig manure treatment was evaluated. Alkaline hydrolysis provided high solubilisation values (up to 66.5% of the biomass), augmenting with increasing values of the three studied variables (NaOH concentration, temperature and time). Nevertheless, moderate total (13.2%) and protein extraction yields (16.9%) were obtained, which was attributable to protein denaturation or to the low effectivity of the precipitation method. Extracts rich in proteins (53.5%–77.9%) with suitable amino acid profiles were obtained, but significant amounts of the initial lipids (up to 44.6%) were co-extracted probably due to fatty acids saponification. These results establish the first step for future studies in enhancing cell wall disruption and protein recovery by coupling alkaline hydrolysis with other mechanical pre-treatments, while considering alternative separation and purification methods. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The monoethanolamine increased the amount of dissolved carbon by up to 500%. • The fed-batch culture with monoethanolamine had increased carbon during cultivation. • Fed-batch culture with MEA had increased proteins and lipids of the Chlorella biomass. Abstract The aim of this study was to evaluate the interaction between the periodic addition of monoethanolamine (MEA) and CO 2 during the cultivation of Chlorella fusca LEB 111. For this purpose, MEA has been added in abiotic assays, followed by fed-batch cultures with that green alga and the absorbent. BG-11 medium shown a higher potential of CO 2 absorption with MEA addition, and the bicarbonate was the chemical species of carbon prevailing in the chemical equilibrium. The periodic addition of MEA did not reduce the kinetics of growth, promoted a higher accumulation of DIC (81.4 mg L−1) in the medium and protein (44.0% w w−1) and lipid (30.8% w w−1) concentrations in the biomass of C. fusca LEB 111. Therefore, it was demonstrated that fed-batch culture with MEA increased CO 2 fixation and the biomolecule synthesis as proteins and lipids. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The moisture content of feedstock showed no effect on hydrochar performances. • Carbohydrates were the main contributors to the formation of hydrochar. • Proteins were able to enhance nitrogenous heterocyclic functional groups. • Lipids did not participate in the carbonization reaction. • The main hydrolyzates of lipids were adsorbed to the surface of hydrochar. Abstract This study aims to figure out the influence of moisture content and chemical constitution, i.e. carbohydrates, proteins and lipids, of waste lettuce on the physicochemical structure of hydrochar produced via hydrothermal carbonization. The experimental results showed that homogenized carbon material can be obtained by hydrothermal treatment, regardless of the moisture content of feedstock. During the hydrothermal carbonization process of waste lettuce, carbohydrates were the most active reactants contributing to hydrochar formation. Meanwhile, Maillard reaction between proteins and carbohydrates occurred, which promoted the aromatization of the organic intermediates and increased the relative content of nitrogenous heterocyclic functional groups on the surface of hydrochar from 10.7 to 18.7%. Different from these two constitution, lipids did not participate in the carbonization reaction, the main hydrolyzates of lipids were adsorbed to the surface of hydrochar, leading to an increase in the mass of solid products. [ABSTRACT FROM AUTHOR]

Highlights • Ultrasonic irradiation markedly enhanced the algal biomass and lipid accumulation. • The optimal ultrasonic treatment parameters for lipid production were obtained. • Low-strength ultrasonic stimulation did not damage the integrity of cell structure. • The biomass concentration and lipid content of microalgae increased 26.9% and 37%. Abstract Ultrasonic treatment was applied to enhance the biomass and lipid accumulation of mixotrophic microalgae. The optimal microalgal ultrasonic power, ultrasonic frequency, ultrasonic interval and growth phase were 20 W, 20 Hz, 2 s and logarithmic phase, respectively. The maximum biomass concentration and lipid content reached 2.78 g L−1 and 28.5%, which were 26.9% and 37% higher than those of the control group. Microscope analysis shows that ultrasonic exposure caused tiny cracks or holes on the surface of cell walls, but did not damage the integrity of algal cell structure. After ultrasonic stimulation, the permeability of membrane and the transport of nutrients were improved, and the utilization rate of substrate and pigment concentration increased 22.7% and 18.4%, respectively. However, excessive ultrasonic irradiation significantly inhibited the cell growth and lipid accumulation of microalgae. This study indicates the feasibility and efficiency of using low-strength ultrasound in promoting biomass and lipid production of microalgae. [ABSTRACT FROM AUTHOR]

Highlights • Concurrent production of chitosan and lipids from Mucor circinelloides ZSKP. • Fungal lipid profile showed higher content of unsaturated fatty acids. • Enzymatic transesterification showed more glycerol as the by-product. • Higher cetane number of fungal lipid-derived biodiesel than sunflower oil. Abstract A newly-isolated oleaginous fungus Mucor circinelloides ZSKP concurrently yielded 21.4% lipids and 11.2% chitosan per gram of biomass. Parameters affecting the co-production were identified using Plackett-Burman design and were statistically optimized using Response Surface Methodology, which resulted in a 3-fold improvement in lipid production. The lipid profile showed a high content of unsaturated fatty acids including oleic (37%), linolenic (14%) and linoleic acids (19%), while palmitic acid was the major saturated fatty acid (21%). A comparative study to evaluate the efficacy of enzymatic (lipase) and chemical treatments for biodiesel production from fungal lipids and sunflower oil revealed enhanced production of biodiesel from fungal lipids. Synthesized biodiesel from M. circinelloides ZSKP satisfied standard specifications and had a higher cetane number (56), lower kinematic viscosity (4.6 mm2/s) and lower acid number (0.03) compared to sunflower oil. Results suggest Mucor circinelloides ZSKP is a promising candidate for implementation of the biorefinery concept. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Two strains of non-acidophilic microalgae (NAM) were acclimated to pH 3.0. • Flow cytometry analysis indicated their ability to withstand acidic pH. • Both the acclimated strains yielded good amounts of biomass and neutral lipids. • FTIR analysis confirmed accumulation of more triacylglycerols in NAM strains. • First report on biodiesel production in good amounts by NAM strains at pH 3.0. Abstract The overwhelming response towards algal biodiesel production has been well-recognized recently as a sustainable alternative to conventional fuels. Most microalgae cannot grow well at acidic pH. The present study, therefore, investigated whether non-acidophilic microalgae Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3 can be acclimated to extreme-acidic pH for sustainable production of biomass and biodiesel. Growth analysis indicated that both the microalgal strains possessed a passive uptake of CO 2 at pH 3.0 with biomass production of 0.25 g dry wt. L−1 in Desmodemus sp. and 0.45 g dry wt. L−1 in Heterochlorella sp.. Flow-cytometry analysis for reactive oxygen species, membrane permeability and neutral-lipids revealed the capabilities of both strains to adapt to the stress imposed by acidic pH. Lipid production was doubled in both the strains when grown at pH 3.0. In-situ transesterification of biomass resulted in 13–15% FAME yield in the selected microalgae, indicating their great potential in biofuel production. [ABSTRACT FROM AUTHOR]

Highlights • An efficient way of genome editing using CRISPR-Cas9 in microalgae. • Knockout of a key effector gene in Lands cycle have increased in TAG accumulation. • Increase in overall lipid productivity of the green alga, Chlamydomonas reinhardtii. • Upstream process for reducing the production cost of the microalgal biofuel. Abstract 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 A 2 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 A 2 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. [ABSTRACT FROM AUTHOR]

Highlights • N. oceanica was cultured in 14-L photobioreactors using a three-phase culture system. • Maximum biomass was produced with 24 h blue LED light at an intensity of 250 µmol m−2 s−1. • Maximum lipid content was obtained with 24 h green LED light at an intensity of 250 µmol m−2 s−1. • SFAs were changed to MUFAs and PUFAs at low temperatures (15, 10, and 5 °C). • The highest PUFA content was obtained at a culture temperature of 5 °C. Abstract A three-phase culture system combining blue (465 nm) light-emitting diode (LED) wavelength as the first phase, green (550 nm) as the second phase, and temperature stress as the third phase was applied to a Nannochloropsis oceanica culture in 14-L photobioreactors. Microalgal growth promotion parameters were optimized in the first phase, followed by green LED stress for lipid production in the second phase. Maximum biomass and lipid production values of 0.75 gdcw L−1 and 57.6% (w/w) were obtained at an aeration rate of 0.50 vvm, with a light intensity of 250 µmol m−2 s−1 and 24:0 h light/dark cycle. Culture temperatures of 15, 10 and 5 °C were applied in the third phase, where temperature stress induced the production of monounsaturated and polyunsaturated fatty acid synthesis in N. oceanica. The production of α-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid increased by 52% (w/w), 96% (w/w), and 77% (w/w), respectively, at 5 °C in the third phase. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A heterotrophic-assisted photoautotrophic biofilm growth mode was constructed. • Light penetration capability in the HAPB was 64% stronger than that in the PB. • Nutrients were optimized to improve microalgae biomass and lipid productivity. • Maximum specific growth rate of Chlorella vulgaris increased by 78%. • Lipid content and yield increased by 120% and 147%, up to 47.53% and 41.95 g m−2. Abstract In order to solve the technical bottleneck that the biomass yield and lipid accumulation cannot be increased simultaneously during microalgae growth, a heterotrophic-assisted photoautotrophic biofilm (HAPB) growth mode of Chlorella vulgaris was constructed. The light penetration capability of the microalgae biofilm formed through heterotrophic-assisted photoautotrophic growth was 64% stronger than that formed by photoautotrophic growth. Due to the different demands of autotrophic and heterotrophic growth of microalgae, the nutrient environment and growth conditions were optimized to fully utilize the advantages and potentials of the HAPB culture model. An optimized molar ratio of total inorganic carbon (CO 2) to total organic carbon (glucose) (20:1) and a molar ratio of total carbon to total nitrogen (72:1) were obtained. The maximum specific growth rate of Chlorella vulgaris increased by 78% compared to that before optimization. Meanwhile, the lipid content and yield increased by 120% and 147%, respectively, up to 47.53% and 41.95 g m−2. [ABSTRACT FROM AUTHOR]

Highlights • Mass cultivation of D. salina was optimized in a FP-PBR. • Improved VFP-PBR with semicontinuous cultivation yielded better results. • 0.75 mM of the NaHCO 3 and 10 mM of KNO 3 were optimal values for neutral lipid production. • Harvesting of cells was most effective at pH 9 conditioned with 0.5 mM FeCl 3 ·6H 2 O. Abstract Mass cultivation of Dunaliella salina was standardized in a flat plate photobioreactor followed by a vertical flat plate photobioreactor. Maximum biomass productivity (14.95 ± 0.43 mgL−1d−1 dry cell weight) was achieved in the latter at inoculum concentration of OD 680nm = 0.1, 100 µmolm−2s−1 light illumination and 1.0 L min−1 aeration. Semicontinuous operation with varying KNO 3 and NaHCO 3 concentrations resulted highest biomass productivity (17.85 ± 0.55 mgL−1d−1) at 0.50 mM NaHCO 3 and 15 mM KNO 3. However, maximum lipid (16.36 ± 1.18% dry cell weight) was achieved at 0.75 mM NaHCO 3 and 10 mM KNO 3. Flocculation studies employing potash alum, FeCl 3 ·6H 2 O or pH showed harvesting efficiencies exceeding 90% in 0.75 mM potash alum or FeCl 3 ·6H 2 O or pH 11, but they yielded low concentration factor (<5) and were detrimental (Fv/Fm < 0.50). A combination of 0.50 mM FeCl 3 ·6H 2 O and pH 9 was found as most suitable flocculating strategy with maximum concentration factor (>14) and least damaging (Fv/Fm > 0.54). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Microalgae incubation after PEF-treatment improves water-soluble components release. • Microalgae incubation after PEF-treatment improves lipid extraction yields. • With 20 h of incubation, energy of PEF-treatment can be reduced to 0.25 MJ/kg DW. • Incubation is also efficient at 4 °C but less than at 25 °C. Abstract Pulsed Electric Field (PEF) pre-treatment, applied on fresh microalgae Auxenochlorella protothecoides, induces spontaneous release of a substantial water fraction and enables subsequent lipid extraction using ethanol-hexane blends. In this study, fresh microalgae suspensions were treated with PEF and incubated under inert conditions. Incubation promotes the release of ions and carbohydrates and increases the yields of subsequent lipid extraction thus enabling a considerable reduction of PEF-treatment energy. With a 20 h incubation period at 25 °C, almost total lipid extraction is achieved with a specific PEF-treatment energy of only 0.25 MJ/kg DW. Incubation on ice remains beneficial but less efficient than at 25 °C. Additionally, incubating microalgae cells in suspension at 100 g DW /L or in a dense paste, was almost equally efficient. Correlation between the different results suggests that spontaneous release of ions and carbohydrates facilitates more successful lipid extraction. A direct causality between the two phenomena remains to be demonstrated. [ABSTRACT FROM AUTHOR]

Highlights • Swine slaughterhouse waste produced a maximum methane yield of 999.2 mL/g VS. • Lipid hydrolysis led to serious accumulation of linoleic, oleic and palmitic acids. • Increase of palmitic acid produced by degradation of oleic acid was observed. • Predominant microorganisms were Clostridium , Syntrophomonas and Methanospirillum. Abstract This study investigated methane production, long-chain fatty acids (LCFAs) profile, and predominant microorganisms in anaerobic digestion (AD) of lipid-rich swine slaughterhouse waste (SSW). The maximum methane yield was 999.2 mL/g VS. LCFAs, as inhibitory hydrolysis products, accumulated first to 1165 mg/L on day 3, and then decreased sharply to 125.7 mg/L on day 9, and finally were degraded to 20 mg/L on day 27. Linoleic acid (C18:2), oleic acid (C18:1) and palmitic acid (C16:0) were the dominant LCFAs. The easy conversion of C18:1 to C16:0 compared with difficult degradation of C16:0 resulted in an increase of C16:0 on day 4–6. Predominant microorganisms were Clostridium , Syntrophomonas and Methanospirillum. This study proved the high methane potential of lipid-rich SSW and gained insights into the degradation process by analysis of intermediates of LCFAs and predominant microorganisms. The results can provide valuable guidance for efficient utilization of this waste to produce methane in future. [ABSTRACT FROM AUTHOR]

Highlights • We develop a new quadruple substrate kinetic model of microalgal cultivation. • The model accounts for substrate, nutrient, temperature & light intensity dynamics. • We experimentally validate the model through a series of lab-scale experiments. • We use the model to compute optimal conditions to maximise lipid productivity. • We validate experimentally the computed optimal growth parameters. Abstract This paper presents a new quadruple-factor kinetic model of microalgal cultivation considering carbon and nitrogen concentration, light intensity and temperature, developed in conjunction with laboratory-scale experiments using the well-studied chlorophyte microalgal species Chlamydomonas reinhardtii. Multi-parameter quantification was exploited to assess the predictive capabilities of the model. The validated model was utilized in an optimization study to determine the optimal light intensity and temperature for achieving maximum lipid productivity while using optimal acetate and nitrogen concentrations (2.1906 g L−1 acetate and 0.0742 g L−1 nitrogen) computed in a recent publication. It was found that the optimal lipid productivity increased by 50.9% compared to the base case, and by 13.6% compared to the previously computed optimal case. Optimization results were successfully validated experimentally. Such comprehensive modelling approaches can be exploited for robust design, scale-up and optimization of microalgal oil production, reducing operating costs and bringing this important technology closer to industrialization. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Efficacy of quercetin (Qn) on biomass and lipid was established in C. vulgaris. • Qn potentiates biomass and lipid enhancement despite nitrogen concentration. • Qn improves antioxidant potential of the cells. • Transcriptomic and UPLC-QTOF-MS data uncover the role of Qn in signaling pathway. • Qn hyperaccumulated cellular biomass and lipid by 2.5- and 1.8-fold, respectively. Abstract Provision of chemical modulators has emerged as an effective strategy to govern cell growth and development. Here, the impact of flavonoid quercetin on algal growth, lipid accumulation and transcriptional patterns was investigated in the green microalga Chlorella vulgaris. These results demonstrated that quercetin (15 μg/l) significantly enhanced the cellular biomass and photosynthetic efficiency, with up to 2.5-fold in the biomass in the stationary phase. Lipidomic analyses revealed that lipid content was increased by 1.8-fold. Furthermore, the functional mechanism of quercetin on the molecular level was dissected by transcriptomic analysis. Results revealed that quercetin upregulated the expression pattern of key genes involved in cellular signaling mechanisms such as phosphatidylinositol 4-kinase α, thus consequently enhanced cell growth. Altogether, the data present in this study demonstrate the dramatic role of quercetin on enhancing microalgal biomass and lipid accumulation by unprecedented regulation, of key metabolic nodes, for the first time and provide a novel insight into microalgal metabolism and regulation. [ABSTRACT FROM AUTHOR]

Adoption of microalgae-sourced products depends on the economic feasibility. In the case of fatty acids, it is crucial to obtain high lipid yield, especially in the form of storage lipids (TAGs). However, the production of these lipids often comes into competition with the microalgae biomass, resulting in a decrease in growth. A microalgae culture integration project was conducted in an industrial park in Canada in order to cultivate microalgae from park’s wastewaters and then obtain products from the biomass. Different deficiencies and stresses were tested to evaluate what condition allowed the induction of the highest lipids accumulation without compromising the growth of microalgae. The results showed that the medium controlled to pH 7.0 allowed reaching the largest amount of extracted lipids (28 ± 4.3%). Companies involved in this project could be able to make significant savings by the reduced wastewater treatment costs and by not adding expensive nutrients in culture. [ABSTRACT FROM AUTHOR]

In this study, the effect of glycerol kinase overexpression in Synechocystis sp. PCC 6803 on lipid content was investigated. The glycerol kinase overexpressing Synechocystis cells (OE) had a higher lipid content than the wild type. The OE treated with phenol up to 1 mM showed a slight increase in the cell biomass whereas the total lipid production increased considerably (0.39 ± 0.012 g/L) as compared to that of the wild type (0.26 ± 0.01 g/L). The supplementation of 12 g/L glycerol to BG11 medium increased the lipid content of phenol treated OE from 22 to 35% with the increase of lipid production from 0.39 ± 0.012 to 0.69 ± 0.035 g/L. The RT-PCR analysis revealed that the expression of glpK was upregulated from 1.3 to 2.4 and from 1.89 to 3.64-fold after phenol treatment and glycerol supplementation respectively. [ABSTRACT FROM AUTHOR]

Low concentrations of acetic acid were used as carbon source to cultivate Cryptococcus curvatus MUCL 29819 for lipid production under high content of ammonia. Phosphorus limitation combined with initial pH regulation (pH = 6) weakened inhibition of free ammonia and promoted lipid accumulation. In batch cultivation, the produced lipid content and yield was 30.3% and 0.92 g/L, higher than those under unlimited condition (18.3% and 0.64 g/L). The content of monounsaturated fatty acid also increased from 37.3% (unlimited condition) to 45.8% (phosphorus-limited condition). During sequencing batch cultivation (SBC), the lipid content reached up to 51.02% under phosphorus-limited condition while only 31.88% under unlimited condition, which can be explained by the higher conversion efficiency of the carbon source to lipid. The total energy consumption including lipid extraction, transesterification and purification was 7.47 and 8.33 GJ under phosphorus-limited and unlimited condition, respectively. [ABSTRACT FROM AUTHOR]

Acetate and ammonium were used as organic carbon and nitrogen sources, respectively, during mixotrophic cultivation of Chlorella pyrenoidosa . Cell growth, content of neutral lipid (NL), productivity of biomass and total lipid, and fatty acid profiles were investigated. Results showed that C. pyrenoidosa could endure high concentrations of NH 4 + -N (100–200 mg/L) and immediately entered logarithmic growth, when the culture media contained 2.0–10.0 g/L NaAc. The 2.0–10.0 g/L NaAc in the media also resulted in the NL content of 1.87–3.05 mg/10 9 cells, much higher than 0.5 mg/10 9 cells of the controls. The maximum productivities of biomass and total lipid were achieved under 50 and 10 mg/L NH 4 + -N respectively when the 2.0 g/L NaAc was dosed. The fatty acids were mainly composed of C16:0, C16:1, C18:0, and C18:1 under the mixotrophic cultivation, with the higher saturation compared to the controls. [ABSTRACT FROM AUTHOR]

Schizochytrium sp. is a promising candidate for docosahexaenoic acid (DHA) production due to its high content of lipid and DHA proportions. To further enhance the lipid accumulation, seven chemical modulators were screened to evaluate their roles on lipid accumulation. Notably, among the seven tested chemical modulators, the addition of naphthoxyacetic acid (BNOA) or jasmonic acid (JA) was able to increase the lipid accumulation of Schizochytrium sp. S31. In addition, the effects of BNOA and JA were demonstrated dose-dependent and time-dependent, achieving a highest increase in lipid content by 11.16% and 12.71% when 2.0 mg/L of BNOA or 20 mg/L of JA was added into culture at 48 h after inoculation, respectively. In addition, the combination of 2 mg/L BNOA and 20 mg/L JA further increased lipid accumulation up to 16.79%. These results provided valuable strategy on promoting the lipid accumulation and DHA production by chemical modulators in Schizochytrium sp. S31. [ABSTRACT FROM AUTHOR]

In this study, melatonin (MT) promoted lipid accumulation in Monoraphidium sp. QLY-1 under nitrogen deficiency conditions. The lipid accumulation increased 1.22- and 1.36-fold compared with a nitrogen-starved medium and a normal BG-11 medium, respectively. The maximum lipid content was 51.38%. The reactive oxygen species (ROS) level in the presence of melatonin was lower than that in the control group, likely because of the high antioxidant activities. The application of melatonin upregulated the gibberellin acid (GA) production and rbcL and accD expression levels but downregulated the abscisic acid (ABA) content and pepc expression levels. These findings demonstrated that exogenous melatonin could further improve the lipid production in Monoraphidium sp. QLY-1 by regulating antioxidant systems, signalling molecules, and lipid biosynthesis-related gene expression under nitrogen deficiency conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Exogenous GAs promoted the metabolism of SMX by C. vulgaris. • When the GAs dose reached 50 mg/L, 91.8 % of SMX was removed. • GAs promoted the production of lipid by microalgae under antibiotic stress. • GAs promoted C. vulgaris to increase antioxidant enzyme activity under SMX stress. • Transcriptome analysis revealed the molecular mechanism of GAs action. In this study, the phytohormone gibberellins (GAs) were used to enhance sulfamethoxazole (SMX) removal and lipid accumulation in the microalgae Chlorella vulgaris. At the concentration of 50 mg/L GAs, the SMX removal achieved by C. vulgaris was 91.8 % while the lipid productivity of microalga was at 11.05 mg/L d-1, which were much higher than that without GAs (3.5 % for SMX removal and 0.52 mg/L d-1 for lipid productivity). Supplementation of GAs enhanced the expression of antioxidase-related genes in C. vulgaris as a direct response towards the toxicity of SMX. In addition, GAs increased lipid production of C. vulgaris by up-regulating the expression of genes related to carbon cycle of microalgal cells. In summary, exogenous GAs promoted the stress tolerance and lipid accumulation of microalgae at the same time, which is conducive to improving the economic benefits of microalgae-based antibiotics removal as well as biofuel production potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stable performance was achieved in treating 10% to 14% high-solid lipids and FW. • High lipid removal owing to over 95% degradation and 100% membrane rejection. • The co-digestion of lipid and FW achieved significant biogas production. • The membrane fouling rate was decreasing with lipids ratio increasing. The co-digestion performance of mesophilic (37℃) hollow fiber anaerobic membrane bioreactor (HF-AnMBR) in treating high-solid lipids and food waste (FW) for 180 days was investigated. The organic loading rate (OLR) was increased from 2.33 to 14.64 g-chemical oxygen demand (COD) /L/d by increasing the lipids/FW from 10%, 30%, and 50% on dry based. The COD conversion efficiency for methane was 83.13%, 84.85%, 82.63%, and 84.30%, and the sludge growth rate was 0.001, 0.097, 0.065, 0.016 g TS/g COD at OLR of 2.33, 9.36, 12.76 and 14.64 g-COD/L/d, respectively. The COD, proteins, and carbohydrates concentrations in permeate were stable, with an average of 2.25, 0.50, and 0.18 g/L, respectively. The long-term stable performance of the HF-AnMBR indicated that this study will help guide application of the co-digestion of lipids and food waste. [ABSTRACT FROM AUTHOR]