For efficient production of microbial lipids also known as single cell oil (SCO), selection of favorable growth conditions including the substrate for maximum conversion into storage lipids is imperative. Utilization of lignocellulosic biomass for microbial oil production is a promising approach as it is renewable, sustainable, and available in abundance, with a significant quantity of fermentable sugars. Because of their intricate structure and biomolecular composition, lignocellulosic substrates exhibit high recalcitrance and demand specific pretreatments to release the fermentable sugars. However, pretreating the lignocellulosic substrate not only produces assimilable sugars but also various fermentation inhibitors that can significantly impede microbial growth and/or lipogenesis. Therefore, in this review, we discuss different inhibitors present in the lignocellulosic hydrolysates, and the impact on oleaginous microbial growth and metabolic activity, particularly concerning lipid production. Furthermore, the mode of inhibition of the various inhibitors and potential strategies to detoxify these are discussed in this review.

Inhibition of Aspergillus flavus growth and its aflatoxins production using the biocontrol agent Saccharomyces cerevisiae as well as to explore its mode of action was studied. Eight strains of S. cerevisiae strains were able to suppress the growth of A. flavus Z103. The maximum growth inhibition of A. flavus Z103 was obtained by living cells of S. cerevisiae EBF101 and S. cerevisiae 117 with 85 and 83%, respectively. The sporulation inhibition and hyphae deterioration of A. flavus Z103 by S. cerevisiae cells adhesion were observed under SEM; up to 99·8% inhibition of aflatoxins biosynthesis by A. flavus Z103 was resulted when the fungus was treated by autoclaved extracellular crude of S. cerevisiae. Also, the tested strains are potential to produce exo‐chitinase which could be suggested as another mode of action for its antifungal activity. GC‐MS analysis of S. cerevisiae 117 extracellular secondary metabolites revealed the existence of 4‐Hydroxyphenethyl alcohol (46·32%), 4, 4‐Dimethyloxazole (9·14%) and 1,2‐Benzenedicarboxylic acid dioctyl ester (2·8%). Significance and Impact of the Study: The use of Saccharomyces cerevisiae instead of chemical preservatives in fermented food, animal and fish feed and storage cereal grains could encourage the food industry to produce organic food free of chemical additives. Overall, our data suggest the possibility of using S. cerevisiae as an alternative treatment in the food industries to control the dispersion and aflatoxins production by Aspergillus flavus during storage. This method could provide an additional probiotic effect in the digestive tract of consumers after ingestion of the treated food. So, our study clarifies the exact mechanisms responsible for the reduction of the aflatoxin contents by S. cerevisiae

Aims The present work aims to explore a new oleaginous Fusarium isolate potential to accumulate lipids in its biomass from inexpensive substrates. In addition, impacts of crabon and nitrogen sourses and their ratios on lipid production by the interested fungal isolate were also conducted. Methods and Results Lipid was assayed by sulfo‐phosphor‐vanillin (SPV) colorimetric method. Among eleven Fusarium isolates obtained onto potato dextrose agar (PDA) from rhizosphereic soils, Fusarium RAS18 was selected as the highest producer that accumulates above 20 % lipid. It was identified based on phenotypic characterization and the Internal Transcribed Spacer (ITS) sequence as Fusarium solani, that was recorded in the GenBank database under the accession number MK167372.1. The optimized lipids yield (34·5 %) is obtained on glycerol (35 gl^‐1) and peptone (1·5 gl^‐1) as carbon and nitrogen sources, respectively. The produced fatty acid methyl esters (biodiesel) is composed of linoleic acid (56·81%), palmitic acid (17·81%), oleic acid (11·81%) and stearic acid (11·12). The unsaturated fatty acids accounted 69% and this is nearly similar to the plant oils commonly used in biodiesel production. Conclusions These findings suggest the applicability of Fusarium solani RAS18 as a promising strain to accumulate lipids from glycerol as a feedstock for biodiesel production. Significance and Impact of the Study Fusarium solani RAS18 is a new oleaginous fungal isolate that is able to produce lipid (34·5 %, gg^‐1) from glycerol. Glycerol is a cheap substrate and is formed as a byproduct from transesterification process and others industries. Thus, recyclation of glycerol for lipid production by microorganisms is an important point of economic view. Direct transesterification of the produced fatty acids indicated its similarity to the plant oil composition that used in biodiesel production. So, F. solani RAS18 might be a potential tool for lipid as a feedstock for biodiesel production.

Background: Biohydrogen production from agro-industrial wastes through dark fermentation offers several advantages including eco-friendliness, sustainability, and the simplicity of the process. This study aimed to produce biohydrogen from fruit and vegetable peel wastes (FVPWs) by anaerobic fermentative bacteria isolated from domestic wastewater. Kinetic analysis of the produced biohydrogen by five isolates on a glucose medium was analyzed using a modified Gompertz model (MGM). Besides, the feasibility of hydrogen production by Clostridium butyricum NE95 using FVPWs as substrates was investigated. Results: The bacterial isolate NE95 was selected as the highest biohydrogen producer with maximum biohydrogen production (H_max) of 1617.67 ± 3.84 mL/L, R_max (MGM) of 870.77 mL/L/h and lag phase (λ) of 28.37 h. NE95 was phenotypically and genetically identified as C. butyricum and its 16 S rRNA gene sequence was deposited in the GenBank under the accession number PP581833. The genetic screening of hydrogenase gene clusters indicated the presence of Fe-Fe hydrogenase gene in C. butyricum NE95. C. butyricum NE95 showed the ability to produce biohydrogen from different FVPWs, with watermelon and melon peels being the most promising feedstocks for fermentation. It was revealed that using a mixture (1:1, w/w) of watermelon and melon peels as a substrate for C. butyricum NE95 significantly increased biohydrogen yield with H_max of 991.00 ± 10.54 mL/L, R_max of 236.31 mL/L/h, λ of 33.92 h and a high accuracy of R² (0.997). Conclusions: The study highlights the effectiveness of C. butyricum NE95 on the valorization of FVPWs and generates a sustainable source of biohydrogen production.

A total of 56 Gram negative bacterial isolates were recovered from twenty ground beef samples and were screened for their potentiality to produce lipase. Forty four bacterial isolates were recorded as positive producers for lipase on tween as carbon source in solid medium. Also, the highly producer isolates were screened for lipase activity in submerged culture using olive oil as carbon and the most active isolate was 2043 which gave an activity of 20.0 ± 0.29 U/ml. The bacterial isolate 2403 was identified phenotypically according to Bergey’s Manual and genotypically using 16S rRNA genes analysis as Pseudomonas monteilli. Effect of some different factors on lipase activity were studied and the maximum lipase activity was achieved at reaction medium of pH 6 and incubated at 40°C for 60 min. Also, addition of Ba2+ in the reaction medium enhanced the lipase activity, while the other tested metals reduced the enzyme activity. Key words: Food contamination, lipase activity, olive oil, cultural conditions, Pseudomonas.