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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]