Transcriptome Mechanism of Utilizing Corn Steep Liquor as the Sole Nitrogen Resource for Lipid and DHA Biosynthesis in Marine Oleaginous Protist Aurantiochytrium sp

Turning waste into treasure: A new direction for low-cost production of lipid chemicals from Thraustochytrids

Thraustochytrids are marine microorganisms known for their fast growth and ability to store lipids, making them useful for producing polyunsaturated fatty acids (PUFAs), biodiesel, squalene, and carotenoids. However, the high cost of production, mainly due to expensive fermentation components, limits their wider use. A significant challenge in this context is the need to balance production costs with the value of the end products. This review focuses on integrating the efficient utilization of waste with Thraustochytrids fermentation, including the economic substitution of carbon sources, nitrogen sources, and fermentation water. This approach aligns with the 3Rs principles (reduction, recycling, and reuse). Furthermore, it emphasizes the role of Thraustochytrids in converting waste into lipid chemicals and promoting sustainable circular production models. The aim of this review is to emphasize the value of Thraustochytrids in converting waste into treasure, providing precise cost reduction strategies for future commercial production.

Thraustochytrids as a promising source of fatty acids, carotenoids, and sterols: bioactive compound biosynthesis, and modern biotechnology

Thraustochytrids are eukaryotes and obligate marine protists. They are increasingly considered to be a promising feed additive because of their superior and sustainable application in the production of health-benefiting bioactive compounds, such as fatty acids, carotenoids, and sterols. Moreover, the increasing demand makes it critical to rationally design the targeted products by engineering industrial strains. In this review, bioactive compounds accumulated in thraustochytrids were comprehensively evaluated according to their chemical structure, properties, and physiological function. Metabolic networks and biosynthetic pathways of fatty acids, carotenoids, and sterols were methodically summarized. Further, stress-based strategies used in thraustochytrids were reviewed to explore the potential methodologies for enhancing specific product yields. There are internal relationships between the biosynthesis of fatty acids, carotenoids, and sterols in thraustochytrids since they share some branches of the synthetic routes with some intermediate substrates in common. Although there are classic synthesis pathways presented in the previous research, the metabolic flow of how these compounds are being synthesized in thraustochytrids still remains uncovered. Further, combined with omics technologies to deeply understand the mechanism and effects of different stresses is necessary, which could provide guidance for genetic engineering. While gene-editing technology has allowed targeted gene knock-in and knock-outs in thraustochytrids, efficient gene editing is still required. This critical review will provide comprehensive information to benefit boosting the commercial productivity of specific bioactive substances by thraustochytrids.

Lipid Production of Schizochytrium sp. HBW10 Isolated from Coastal Waters of Northern China Cultivated in Food Waste Hydrolysate

Marine oleaginous thraustochytrids have attracted increasing attention for their great potential in producing high-value active metabolites using various industrial and agricultural waste. Food waste containing abundant nutrients is considered as an excellent feedstock for microbial fermentation. In this study, a thraustochytrid strain Schizochytrium sp. HBW10 was isolated from a water column in Bohai Bay in Northern China for the first time. Further lipid production characteristics of S. sp. HBW10 were investigated utilizing sulfuric acid hydrolysate of food waste (FWH) from two different restaurants (FWH1 and FWH2) with the initial pH value adjusted by NaOH or NaHCO3. Results showed that the highest concentration of total fatty acids (TFAs) was observed in FWH2 medium with the 50% content level on the fifth day, reaching up to 0.34 g/L. A higher initial pH promoted the growth and saturated fatty acid (SFA) accumulation of S. sp. HBW10, achieving nearly 100% of the sum of saturated and monounsaturated fatty acids (SMUFAs) in TFAs with initial pH7 and pH8 in FWH1 medium. This work demonstrates a possible way for lipid production by thraustochytrids using food waste hydrolysate with a higher initial pH (pH7~pH8) adjusted by NaHCO3.

Metagenomic Analysis of Bacterial, Archaeal and Fungal Diversity in Two-Stage Anaerobic Biodegradation for Production of Hydrogen and Methane from Corn Steep Liquor

The main purpose of this study was to identify the microbial communities (bacterial, archaeal and fungal) in a two-stage system of anaerobic bioreactors for the production of hydrogen and methane from the waste substrate-corn steep liquor. Wastes from the food industry are valuable resources with potential in biotechnological production because of their high organic matter contents. In addition, the production of hydrogen and methane, volatile fatty acids, reducing sugars and cellulose content was monitored. Two-stage anaerobic biodegradation processes were performed by microbial populations in the first hydrogen generating bioreactor (working volume of 3 dm³) and in the second methane-generating reactor (working volume of 15 dm³). Cumulative hydrogen yield reached 2000 cm³ or 670 cm³/L a day, while the methane production reached a maximum quantity of 3300 cm³ or 220 cm³/L a day. Microbial consortia in anaerobic digestion systems play an essential role for process optimization and biofuel production enhancement. The obtained results showed the possibility of conducting two separate processes-the hydrogenic (hydrolysis and acidogenesis) and methanogenic (acetogenesis and methanogenesis)-as two stages of anaerobic digestion to favor energy production under controlled conditions with corn steep liquor. The diversity of microorganisms as main participants in the processes in the bioreactors of the two-stage system was followed using metagenome sequencing and bioinformatics analysis. The obtained metagenomic data showed that the most abundant phylum in both bacterial communities was Firmicutes-58.61% and 36.49% in bioreactors 1 and 2, respectively. Phylum Actinobacteria were found in significant quantities (22.91%) in the microbial community in Bioreactor 1, whereas in Bioreactor 2, they were 2.1%. Bacteroidetes are present in both bioreactors. Phylum Euryarchaeota made up 0.4% of the contents in the first bioreactor and 11.4% in the second. As the dominant genera among methanogenic archaea are Methanothrix (8.03%) and Methanosarcina (3.39%), the main fungal representatives were Saccharomyces cerevisiae. New knowledge of anaerobic digestion mediated by novel microbial consortia could be widely used to convert different wastes to green energy.

Current advances for omics-guided process optimization of microbial manufacturing

Currently, microbial manufacturing is widely used in various fields, such as food, medicine and energy, for its advantages of greenness and sustainable development. Process optimization is the committed step enabling the commercialization of microbial manufacturing products. However, the present optimization processes mainly rely on experience or trial-and-error method ignoring the intrinsic connection between cellular physiological requirement and production performance, so in many cases the productivity of microbial manufacturing could not been fully exploited at economically feasible cost. Recently, the rapid development of omics technologies facilitates the comprehensive analysis of microbial metabolism and fermentation performance from multi-levels of molecules, cells and microenvironment. The use of omics technologies makes the process optimization more explicit, boosting microbial manufacturing performance and bringing significant economic benefits and social value. In this paper, the traditional and omics technologies-guided process optimization of microbial manufacturing are systematically reviewed, and the future trend of process optimization is prospected.