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An effective prototype of photobioreactor namely hollow fiber membrane bioreactor is employed to produce algal biomass for biofuel production. The effect of two-stage cultivation system on the biomass productivity and lipid production is studied using freshwater green microalga Tetradesmus obliquus MT188616.1. The hybrid system combines exponential biomass production in hollow fiber membrane photobioreactor (HFMPBr) and a coordinated high-lipid stimulation phase in nitrogen-deprived medium by the shake flask method. This work is proposed to examine the usefulness of HFMPBr module to enhance the microalgal growth rate through the effective mass transfer by standardizing the culture medium re-circulation flow rates (5 – 45 mL min−1) through the hollow fiber membranes. Cultivation is carried out at continuous mode in HFMPBr containing polysulfone fabricated membranes at fixed light intensity of 50 µmol m−2 s−1 and temperature at 28 °C. Biomass productivity and specific growth rate obtained are 0.44 g L−1d−1 and 1.61 µ d−1 with a lipid yield of 0.1 g L− 1. The key operating parameter i.e., liquid flow rate is optimized based on biomass production. The highest biomass concentration is produced at the flow rate of 45 mL min−1. The results showed that HFMPBr module is a better choice for the algal-cultivation to obtain higher biomass yield. The effect of two-stage cultivation system on the growth rate, biomass productivity, and lipid yield was studied in freshwater green microalga Tetradesmus obliquus MT188616.1. The hybrid system combines exponential biomass production in hollow fiber membrane photobioreactor (HFMPBr) and a coordinated high-lipid stimulation phase in nitrogen deprived medium by the shake flask method. The algal cultivation was carried out at continuous mode in HFMPBr containing polysulfone fabricated membranes at fixed light intensity of 50 µmol m−2 s−1 and temperature at 28 °C. Biomass productivity and specific growth rate obtained were 0.44 g L−1d−1 and 1.61 µ d−1 with a lipid yield of 0.1 g L− 1. The key operating parameter i.e., liquid flow rate was optimized based on biomass production. The highest biomass concentration was produced at the highest flow rate of 45 mL min−1, whereas the lowest biomass was at the lowest flow rate of 5 mL min−1. The results showed that HFMPBr module was a better choice for the cultivation of Tetradesmus obliquus MT188616.1 to obtain higher biomass yield. [Display omitted] • Integrated HFMPBr and shake flask approach to attain higher lipid yield of algae. • Optimized salt medium flow rate in HFMPBr for continuous algal growth. • Attained efficient delivery of nutrients via membranes for algal growth and waste removal by maintaining optimal flow rate. • Achieved close to 0.44 gL-1day-1 biomass productivity under 45 mL min-1 flow rate during 10 h light – 14 h dark photoperiod. [ABSTRACT FROM AUTHOR]

In order to improve the production and quality of lipid of D. intermedius Z 8 under the furfural stress environment, different exogenous γ-aminobutyric acid (GABA) addition strategies and their reasons for improving the fermentation performance were investigated. For this purpose, the effect of different concentrations of furfural on the production of biomass and lipid in D. intermedius Z 8 was researched. The result shows that the growth of D. intermedius Z 8 nearly stopped when 1.0 g/L furfural was adopted. However, when 1.5 mmol/L GABA was used, the highest biomass and lipid production of 4.56 g/L and 1.83 g/L were obtained, respectively, which were 36.53 % and 61.95 % higher compared to the control group (the normal development BG11 medium). Additionally, the changes in microalgal cell morphology were analyzed using the scanning electron microscope (SEM) technology, and the results suggest that GABA addition could significantly mitigate the toxic effects of excessive furfural by maintaining the integrity of the cell. Simultaneously, the activities of key enzymes involved in fatty acid synthesis, such as nitrate reductase (NR), phosphatidic acid phosphatase (PAP), acetyl CoA carboxylase (ACC), and fatty acid synthase (FAS), were enhanced under the optimal condition, and thus improving lipid production. According to the results in this study, the exogenous GABA addition strategy is a simple and effective approach to improve microbial tolerance and enhance its fermentation performance., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Toxic cyanobacterial blooms are recurrent for few decades throughout the globe, due to climate change, atmospheric warming and various anthropogenic activities with severe impacts of potential toxins on various ecosystems finally affecting the entire environment. These cyanobacteria are merely unexplored regarding their biochemical components except toxins. Variable influences and interactions of different factors including nitrogen, carbon, and availability of light are well known to crucially regulate cyanobacterial growth and metabolism. Thus, current research work is motivated for the evaluation and optimization of the effects of the aforementioned vital factors for improvement of biomass and lipid production of a freshwater, toxic strain of Anabaena circinalis. The modelling and optimization of factors such as nitrogen, light intensity and bicarbonate concentration (source of carbon) to maximize growth and lipid production were based on 20 design point experiments by Response Surface Methodology (RSM) and optimized values were further improved and validated by Particle Swarm Optimization (PSO) algorithm. The maximum optima were obtained 1.829 g L-1 and 39.64 % for biomass production and lipid content respectively from PSO optimization with two different sets of optimal values of factors. It shows 0.44 % and 2.77 % higher values of responses than that of RSM optimization. These asynchronous findings pioneered the enhanced lipid accumulation as well as the growth of a toxic cyanobacterium by optimizing interaction effects of culture conditions through various statistical and computational approaches. • Influencing factors were optimized for the improvement of biomass and lipid production. • RSM was used to optimize the system parameters and validated by PSO algorithm. • Maximum optima were obtained as 1.829 g L-1 and 39.64 % for biomass production. • Results shows that 0.44 % and 2.77 % higher values than that of RSM optimization. [ABSTRACT FROM AUTHOR]

Biodiesel, as a renewable and eco-friendly energy source that can be produced through algae oil esterification, has recently received much attention. Maximization of algal biomass and lipid content is crucial for commercial biodiesel production. In this study, Chlorella sp. PG96, a microalgal strain isolated from urban wastewater, was identified considering its morphological and molecular characteristics. Fractional factorial design (2 11 - 7) was employed to screen medium and environmental factors for achieving high lipid productivity. The effects of eleven factors including light intensity, light spectrum, aeration rate, temperature, salinity, NaHCO 3 , CO 2 , NaNO 3 , NH 4 Cl, MgSO 4.7H 2 O, and K 2 HPO 4 and their interactions on growth characteristics of Chlorella sp. PG96 (biomass and lipid production) were statistically assessed. Based on the experimental results, lipid productivity was at its maximum (54.19 ± 8.40 mg lipid L−1 day−1) under a combination of high levels of all factors. The analysis also showed that physical parameters of light intensity and temperature were more effective on algal growth compared to nutritional parameters. Furthermore, nitrogen source of ammonium and carbon source of bicarbonate played more significant roles in biomass and lipid production, compared with nitrate and CO 2 , respectively. Although the effect of sulfur limitation on cellular growth was similar to phosphorus deficiency, S-limitation had a greater impact on lipid accumulation. The interaction between NaHCO 3 and NH 4 Cl was the most prominent interaction affecting all responses. It is concluded that Chlorella sp. PG96 at a high level of light intensity and temperature (22500 Lux and 32 °C, respectively) can be a prospective candidate for biodiesel production. [Display omitted] • Chlorella sp. PG96 was found to be a suitable candidate for biodiesel production. • FFD (2 11 - 7) successfully determined combined effects of 11 factors on algal growth. • Maximum lipid productivity was obtained at high levels of all factors. • Light intensity and temperature had the most impact on biomass and lipid. • Interaction between NaHCO 3 and NH 4 Cl was the most effective term for all responses. [ABSTRACT FROM AUTHOR]

• First report of lipids production in the marine diatom Chaeotceros affinis. • Palm oil mill effluent (POME) was sole source of N, P and other trace elements. • POME growth media were compared with a standard control medium. • Biomass grown in a vitamins-free POME medium exceeded 48 % in lipids content. • Lipid productivity exceeded 16 mg L–1 d –1 in a 18-day batch culture. Biomass and lipid production by the marine diatom Chaetoceros affinis were characterized under continuous light with aeration. Media based on palm oil mill effluent (POME; 10, 20 and 30 % v/v in distilled water) were used together with a standard control medium. The maximum biomass concentration on day 12 of batch cultures in control medium was 821 ± 71 mg L–1. Under identical conditions, in the best POME medium (20 % POME v/v in distilled water with other inorganic components), the biomass concentration was reduced by ∼11 % to 734 ± 66 mg L–1. The lipid content of the biomass grown in the control medium was 50.8 ± 4.5 % by dry weight, but was a little lower (48.9 ± 4.1 % by dry wt) in the above specified best POME medium. In the best POME medium, oleic acid was the major fatty acid (72.3 ± 5.2 % by weight) in the total lipids extracted from the biomass and monounsaturated fatty acids were the main type of fatty acids (74.6 ± 5.2 %). POME levels of >20 % in the medium suppressed both biomass and lipid production relative to the medium with 20 % POME. [ABSTRACT FROM AUTHOR]

Highlights • Lipid-rich biomass of Rhodococcus opacus could be grown on molasses. • Inhibition by molasses was overcome to displace expensive pure C-substrates. • Lipid content of microbial biomass exceeded 35% w/w after 170 h of culture. • Osmotic stress and other factors enhanced the lipid content in the biomass. Abstract Rhodococcus opacus PD630 was used to produce biomass and lipids in molasses-based media with and without osmotic stress. In a 7-day aerobic batch culture at 30 °C, the biomass and lipid concentrations were maximized using an initial molasses concentration of 80 g/L and ammonium acetate (nitrogen source) concentration of 2.14 g/L. At a fixed initial molasses concentration of 80 g/L, the concentration of the nitrogen source was further fine-tuned to 2.25 g/L, to maximize the lipid content of the biomass to around 30% by dry mass. This medium was used to test the effects of stressing salts (sodium acetate, magnesium sulfate, sodium chloride) on production of lipids and biomass. A two-step bolus feeding with magnesium sulfate and sodium acetate, enhanced the final biomass concentration to around 19 g/L (a 50% increase relative to control), but the lipid content in the biomass was reduced to around 16% w/w. A 33% enhancement in lipid concentration relative to control, was achieved by feeding magnesium sulfate and sodium acetate. Sugarcane molasses could be effectively used to produce biomass and lipids instead of using the much more expensive pure carbon sources such as glucose and sucrose. [ABSTRACT FROM AUTHOR]

The yeast Rhodosporidium toruloides has been extensively studied for its application in biolipid production. The knowledge of its metabolism capabilities and the application of constraint-based flux analysis methodology provide useful information for process prediction and optimization. The accuracy of the resulting predictions is highly dependent on metabolic models. A metabolic reconstruction for R. toruloides metabolism has been recently published. On the basis of this model, we developed a curated version that unblocks the central nitrogen metabolism and, in addition, completes charge and mass balances in some reactions neglected in the former model. Then, a comprehensive analysis of network capability was performed with the curated model and compared with the published metabolic reconstruction. The flux distribution obtained by lipid optimization with flux balance analysis was able to replicate the internal biochemical changes that lead to lipogenesis in oleaginous microorganisms. These results motivate the development of a genome-scale model for complete elucidation of R. toruloides metabolism. [ABSTRACT FROM AUTHOR]

Yarrowia lipolytica , a model microorganism of oleaginous yeasts with developed sophisticated genetic tools, is able to metabolize a wide range of substrates and accumulate large amounts of lipids. However, there is a lack of literature reporting the metabolic characteristics of Y. lipolytica metabolizing these substrates in a systematic view. In this study, Y. lipolytica was cultivated on a variety of carbon sources, among which cell growth and production characteristics on two representative substrates (glucose and oleic acid) were investigated in detail at metabolomic level. Metabolic pathway abundance was computed to interpret the metabolome data in a straightforward way. The results showed that most pathway abundances decreased in the shift from growth to production phase. Specifically, when cultivated on glucose, abundances of twelve pathways decreased markedly between the growth and lipid production phases, while thirteen pathways reduced and only three pathways increased significantly in abundances on oleic acid. In comparison, for the same cultivation phase only a few pathways exhibited significant changes between glucose-grown and oleic acid-grown cells. This study revealed that the pathway abundance could be used to effectively show the activity changes of pathways, providing a new perspective to employ metabolomics data for understanding cell metabolism and enhancing the production of target metabolites. [ABSTRACT FROM AUTHOR]