Coproduction of single cell protein and lipid from lignocellulose derived carbohydrates and inorganic ammonia salt with soluble ammonia recycling

Single cell protein production of co-culture Kodamaea ohmeri and Lactococcus lactis in corn straw hydrolysate

With the world population continuously increasing, the protein demand will double by 2050. Single cell protein (SCP) derived from lignocellulosic biomass offers a sustainable solution. Many inhibitors are produced during the pretreatment process of lignocellulosic biomass. Inhibitor-rich hydrolysates limit microorganisms cell growth and SCP yields. In this work, we report a co-culture consortium of Kodamaea ohmeri SSK (pentose-utilizing yeast) and Lactococcus lactis LX (probiotic bacterium) that efficiently converts real corn straw hydrolysate into SCP. K. ohmeri SSK can tolerate inhibitors such as furfural, 5-hydroxymethylfurfural (5-HMF), and acetic acid and consume glucose, xylose, and arabinose in real hydrolysate. L. lactis LX showed less growth in monoculture than that of co-culture. The total amino acid content from co-cultured K. ohmeri SSK and L. lactis LX was increased to 331.42 mg/g crude protein, but that of monocultured K. ohmeri SSK was 309.89 mg/g crude protein containing 17 amino acids. This work demonstrates a symbiotic microbial platform can produce SCP from non-detoxified lignocellulosic biomass. The co-culture robust inhibitor tolerance and balanced amino acid profile highlight its potential for industrial-scale protein production. These results will represent an attractive choice cell factory for lignocellulosic substrate utilization and provide a platform for biomass conversion to SCP.

Production of single-cell protein from vinegar residue by Rhodotorula glutinis and techno-economic analysis

Single-cell protein (SCP) is attracting attention due to its high value. This study aimed to produce SCP by Rhodotorula glutinis from vinegar residue (VR). The fermentation conditions were optimized by using glucose and then VR was utilized to produce SCP. The titer of SCP was 32.14 g/L, and the protein content and lipid content were 26.67 % and 7.94 %. The yield of SCP was 0.32 g/g VR. Economic analysis of producing SCP from VR showed that processing 100,000 tons of VR annually can produce 32,140 tons of SCP at a production cost of 1,308.38 USD/ton. Sensitivity analysis revealed that the costs of cellulase and yeast were the main factors influencing the production cost of SCP, accounting for 33.6 % and 51.1 % of the raw material cost. Substituting urea for yeast powder could reduce the production cost of SCP to 761.65 USD/ton. This study provided important insights into the industrial production of SCP from VR.

Industrial Microbial Technologies for Feed Protein Production from Non-Protein Nitrogen

Due to the increasing global demand for feed protein, microbial protein has great potential of being able to feed sustainably. However, the application of microbial protein in the animal cultivation industry is still limited by its high cost and availability on scale. From the viewpoint of industrial production, it is vital to specify the crucial processes and components for further technical exploration and process optimization. This article presents state-of-the-art industrial microbial technologies for non-protein nitrogen (NPN) assimilation in feed protein production. Nitrogen sources are one of the main cost factors in the media used for large-scale microbial protein fermentation. Therefore, the available NPN sources for microbial protein synthesis, NPN utilization mechanisms, and fermentation technologies corresponding to the strain and NPN are reviewed in this paper. Especially, the random mutagenesis and adaptive laboratory evolution (ALE) approach combined with (ultra-) throughput screening provided the main impetus for strain evolution to increase the protein yield. Despite the underlying potential and technological advances in the production of microbial protein, extensive research and development efforts are still required before large-scale commercial application of microbial protein in animal feed.

Characterization of cotton stalk as a lignocellulosic feedstock for single-cell protein production

Cotton stalk, an important by-product of cotton farming, is challenging in lignocellulosic feedstock application due to the limited understanding of their compositional and lignin structural characteristics. This study elucidates the composition of lignocellulose components and fundamental lignin structural features of cotton stalk. Lignocellulosic hydrolysates were prepared from various cotton stalk parts and used for single-cell protein production. As a proof of concept, cotton stalk hydrolysates were successfully converted into single-cell protein using the superior microbial host, Candida utilis ACCC20060, owing to its favorable sugar consumption efficiency and high protein quality. The highest SCP concentration of 5.74 g/L was obtained, yielding 0.23 g/g from the lignocellulose-derived sugars released from cotton stalk roots. This study provides valuable references for cotton stalk utilization toward lignocellulosic feedstock application and introduces a promising microbial host for single-cell protein production from such feedstocks.

Co-production of plant- and microbial- proteins from waste tobacco leaves by optimizing alkaline extraction and strengthening pectin bioconversion

The production of alternative proteins is of great significance in the mitigation of food problems. This study proposes an integrated approach including protein extraction, enzymatic hydrolysis, and fermentation to produce both plant proteins and single-cell proteins as alternative proteins from tobacco leaves, a highly-abundant and protein-rich agricultural waste. Alkaline extraction of proteins before polysaccharide hydrolysis was found to be preferable for increasing the yields of plant proteins and mono-sugars. The combined use of pectinase-rich enzymes from Aspergillus brunneoviolaceus and hemicellulase-rich enzymes from Penicillium oxalicum achieved the release of 80.7 % of the sugars after 72 h. Cutaneotrichosporon cutaneum could simultaneously utilize multiple sugars, including galacturonic acid, in the enzymatic hydrolysate to produce single-cell proteins. Via this approach, 43.54 g crude proteins of high protein contents and rich in essential amino acids can be produced from 100.00 g waste tobacco leaves, providing a promising strategy for its valorization.

Adaptive evolution of Paecilomyces variotii enhanced the biodetoxification of high-titer inhibitors in pretreated lignocellulosic feedstock

High inhibitor concentrations in lignocellulose feedstock negatively affect the degradation rate of biodetoxification strains. This study designed two adaptive laboratory evolutions in solid substrate and liquid medium to boost the biodetoxification capacity of P. variotii to high titers of lignocellulose-derived inhibitors, resulting in two evolved strains AC70 and ZW70. The results showed that the evolutionary adaptation in liquid medium could better boost the acetic acid assimilation compared to that on solid substrate. Transcriptional analysis revealed that the evolved strains exhibited a significant upregulation of adh, acs, ach1, and ackA directly related to the initial steps of acetate and furan aldehydes metabolisms. ZW70 strain can effectively remove the high concentration inhibitors cocktail from the hydrolysates derived from pretreated wheat straw and furfural residues. The biodetoxified hydrolysates by ZW70 were successfully used for cellulose chiral L-lactic acid production with the titers of ∼110 g/L, which were over 20 % higher than that detoxified by parental strain.

Sustainable media feedstocks for cellular agriculture

The global food system is shifting towards cellular agriculture, a second domestication marked by cultivating microorganisms and tissues for sustainable food production. This involves tissue engineering, precision fermentation, and microbial biomass fermentation to establish food value chains independent of traditional agriculture. However, these techniques rely on growth media sourced from agricultural, chemical (fossil fuels), and mining supply chains, raising concerns about land use competition, emissions, and resource depletion. Fermentable sugars, nitrogen, and phosphates are key ingredients derived from starch crops, energy-intensive fossil fuel based processes, and finite phosphorus resources, respectively. This review explores sustainable alternatives to reduce land use and emissions associated with cellular agriculture media ingredients. Sustainable alternatives to first generation sugars (lignocellulosic substrates, sidestreams, and gaseous feedstocks), sustainable nitrogen sources (sidestreams, green ammonia, biological nitrogen fixation), and efficient use of phosphates are reviewed. Especially cellulosic sugars, gaseous chemoautotrophic feedstocks, green ammonia, and phosphate recycling are the most promising technologies but economic constraints hinder large-scale adoption, necessitating more efficient processes and cost reduction. Collaborative efforts are vital for a biotechnological future grounded in sustainable feedstocks, mitigating competition with agricultural land and emissions.

Production of single cell protein from brewer's spent grain through enzymatic saccharification and fermentation enhanced by ammoniation pretreatment

Brewer's spent grain (BSG) is a major low-value by-product of beer industry. To realize the high value application of BSG, this work proposed a strategy to produce single cell protein (SCP) with oligosaccharide prebiotics from BSG, via ammoniation pretreatment, enzymatic hydrolysis, and fermentation. The optimum conditions of ammoniation pretreatment obtained by response surface method were 11 % ammonia dosage (w/w), 63 °C for 26 h. Suitable enzyme and yeast were screened to enhance the conversion of cellulose and hemicellulose in BSG into sugars and maximize the SCP yield. It was shown that using lignocellulolytic enzyme SP from Penicillium oxalicum and Trichosporon cutaneum, about 310 g of SCP with 80 g of arabinoxylo-oligosaccharides were obtained from 1000 g of BSG. This process is low cost, high efficiency, and easy to implement, which has good industrial application prospects.

From anaerobic digestion to single cell protein synthesis: A promising route beyond biogas utilization

The accumulation of a large amount of organic solid waste and the lack of sufficient protein supply worldwide are two major challenges caused by rapid population growth. Anaerobic digestion is the main force of organic waste treatment, and the high-value utilization of its products (biogas and digestate) has been widely concerned. These products can be used as nutrients and energy sources for microorganisms such as microalgae, yeast, methane-oxidizing bacteria(MOB), and hydrogen-oxidizing bacteria(HOB) to produce single cell protein(SCP), which contributes to the achievement of sustainable development goals. This new model of energy conversion can construct a bioeconomic cycle from waste to nutritional products, which treats waste without additional carbon emissions and can harvest high-value biomass. Techno-economic analysis shows that the SCP from biogas and digestate has higher profit than biogas electricity generation, and its production cost is lower than the SCP using special raw materials as the substrate. In this review, the case of SCP-rich microorganisms using anaerobic digestion products for growth was investigated. Some of the challenges faced by the process and the latest developments were analyzed, and their potential economic and environmental value was verified.