Single Cell Protein Production Research Articles

From Waste to Protein: Optimizing Rice Husk Utilization for Sustainable Single Cell Protein Production

The increasing global demand for protein has prompted a search for sustainable and cost-effective alternatives to traditional animal and dairy sources. Single-cell protein (SCP) produced from microorganism’s offers a promising solution due to its high protein content and rapid growth rates. This study addresses the challenge of utilizing rice husk, an abundant yet underutilized agricultural waste in Nigeria, as a substrate for SCP production. Through optimization of the production of SCP using Bacillus sp. AT-b3 and Bacillus sp. CMF 12 as model organisms. Molecular identification through 16S rRNA sequencing confirmed Bacillus sp. AT-b3 and Bacillus sp. CMF 12 as the most potent isolates for SCP production. Optimization studies were conducted using the One-Factor-at-a-Time (OFAT) method to determine the ideal fermentation conditions. The results showed that the optimal temperature for SCP production was 40 °C, with Bacillus sp. AT-b3 demonstrating superior production efficiency. pH optimization revealed that neutral pH (pH 7) was ideal for maximizing SCP production, with Bacillus spp. AT-b3 outperforming Bacillus sp. CMF 12 at this pH. Substrate concentration studies indicated that 2.0% was optimal for SCP production, and incubation time optimization indicated 48 hours as the optimal period for maximum yield. Amino acid profiling of the SCP produced showed significant variations between the two isolates. Bacillus sp. CMF 12 was richer in essential amino acids like Arginine and Methionine, while Bacillus sp. AT-b3 had a higher Glycine content at (p<0.05). The findings of this study suggest that both strains have potential applications in nutritional supplements, with Bacillus sp. AT-b3 being particularly suited for industrial-scale SCP production. This study concludes that Bacillus sp. AT-b3 is an efficient SCP producer under optimal conditions of neutral pH, moderate temperature, and appropriate substrate concentration. Further research is recommended to explore pilot-scale production, alternative substrates, and comprehensive safety assessments.

Nutritional properties of pilot-scale manufactured single-cell proteins from a Corynebacterium glutamicum

ABSTRACT Single-cell proteins (SCPs) derived from microorganisms are sustainable and standard-manufacturable protein sources. Corynebacterium glutamicum is one of the prospective bacteria for SCP production. To evaluate nutritional properties of C. glutamicum-SCP, pilot-scale fermentation (3,000 L) was performed under standard conditions, resulting in 23 kg of SCP in dry weight. This C. glutamicum-SCP had high protein and low-fat contents (22.4% carbohydrates, 60.9% crude protein, and 3.3% crude fat). Its fatty acid profile comprised 0.25% saturated fatty acids, 0.16% unsaturated fatty acids, no trans fatty acids, and no cholesterol. Its total iron content was 9.78 mg/100 g, of which approximately 14.8% was heme iron (1.45 mg/100 g). The Digestible Indispensable Amino Acid Score (DIAAS) of C. glutamicum-SCP was 102, higher than that of soy protein isolate (90), pea protein concentrate (82), house cricket (89), or yellow mealworm (64). In conclusion, C. glutamicum-SCP can be a promising alternative protein source to replace red meat.

Preliminary Study on The Characteristics of Effluent From A Cachoeiro de Itapemirim – ES and Analysis of Possible Biotechnological Treatments

Purpose: The objective of this research was to organize and evaluate physical-chemical parameters of the industrial dairy effluent and to propose viable alternative treatments using biotechnological methods, aiming not only to prepare the effluent for disposal but also to generate value-added products Theoretical framework: With the growth of the population, the food industry sector expands exponentially. Brazil ranks among the top five milk producers globally, with the dairy industry being a significant producer of effluent, generating between 1.1 m³ and 6.8 m³ of effluent per cubic meter of processed milk. Dairy wastewater carries a high pollutant load and requires treatment prior to discharge into water bodies. There is an increasing demand for converting waste into raw materials, prompting research into biotechnological treatments that not only prepare effluent for disposal but also yield products from such waste. Method/design/approach: The data on wastewater characteristics were provided by the dairy itself, and the physicochemical aspects of the effluents over 19 months were interpreted, establishing relationships among key parameters, as well as the ratios BOD/COD, BOD: N and COD: N. The survey of biotechnological treatments was conducted through bibliographic research on Google Scholar, Scielo, Web of Science, and Scopus databases. Results and conclusion: Through the analysis and correlations of the physicochemical characteristics of effluents from the Cachoeiro dairy, it is evident that this type of effluent is rich in low biodegradability organic matter, as the BOD5/COD ratio was less than 0.15 in over 79% of the samples, indicating that physical-chemical treatment is the most appropriate approach for this effluent. The linear correlation coefficient between BOD5 and COD was 0.6, suggesting a weak correlation that does not allow one parameter to be accurately predicted from the other. According to the literature, it is possible to derive biofuels, bioplastics, single cell protein, organic acids, polysaccharides, biosurfactants, and other products from dairy effluent, while also meeting environmental requirements Research implications: Evaluation of optimal treatments based on effluent characteristics and suggestion of alternative treatments aiming to utilize wastewater as a raw material for obtaining secondary products complementary to the industry's focus, in addition to compliance with current disposal regulations. Originality/value: Development of relationships to assist in evaluating effluent treatments and identification of treatments that can reuse this substantial volume of generated waste.

Potato peel as substrate for Single Cell Protein in animal feed by submerged fermentation

Single-cell protein (SCP) has gained attention in scientific research as a vital source of protein in animal feed and human food. Taking into account the importance of SCP, an attempt was made in the current research to grow Rhizopus oligosporus and Saccharomyces cerevisiae biomass by selecting potato peel as a substrate. The potato peel was treated with sulfuric acid to form potato peel hydrolysate following acid hydrolysis. In 1.0-L potato peel hydrolysate, 2.5-g/L KH2PO4, 0.5-g/L MgSO4, 0.5-g/L NaCl, and 10 g/L yeast extract were taken to prepare growth media. The moisture content of potato peel was examined by following standard procedure of the Association of Official Agricultural Chemists (AOAC). The Kjeldahl method was used to determine the protein content, and glucose was examined by using the dinitrosalicylic acid (DNS) method. Optimization of SCP yield was accomplished by following the ‘one factor at a time’ method. The effect of each parameter, such as incubation period, temperature and pH on SCP production was analyzed. Bioreactor scale-up production of SCP was performed in a jar fermenter. To enhance SCP, yield co-culture of Saccharomyces cerevisiae and Rhizopus oligosporus was used in a bioreactor that yielded 19 g/L of SCP. Thus, as a nutritional supplement for living organisms, SCP can effectively fulfill protein scarcity globally.

Optimization strategies for enhanced production of single cell protein: recent advances and perspectives

Optimization strategies for enhanced production of single cell protein: recent advances and perspectives

Recovery of purple non-sulfur bacteria-mediated single-cell protein from domestic wastewater in two-stage treatment using high rate digester and raceway pond

Wastewater resources can be used to produce microbial protein for animal feed or organic fertiliser, conserving food chain resources. This investigation hasemployed thefermented sewage to photoheterotrophically grown purple non-sulfur bacteria (PNSB) in a 2.5 m3 pilot-scaleraceway-pond with infrared light to produce proteinaceous biomass. Fermented sewage with synthetic media consisting of sodium acetate and propionic acids at a surface-to-volume (S/V) ratio of 10 m2/m3 removed 89%, 93%, and 81% of chemical oxygen demand, ammonium nitrogen, and orthophosphate, respectively; whereas respective removal in fermented sewage alone without synthetic media was 73%, 73%, and 72% during batch operation of 120 h. The biomass yield of 0.88–0.95 g CODbiomass /g CODremoved with protein content of 40.3 ± 0.3%–43.9 ± 0.2% w/w was obtained for fermented sewage with synthetic media. The results revealed enhanced possibility of scaling-up the raceway reactor to recover resources from municipal wastewater and enable simultaneous high-rate PNSB single-cell protein production.

Use of hydroponic fertilizers in growth media for Chlorella vulgaris for producing affordable protein in developing countries

ABSTRACT Chlorella vulgaris (Chlorophyta) stands out as a promising microalga for single-cell protein production, particularly due to its potential to address the need for affordable nutrition in less-developed regions. Given this context, the quest for more economic fertilization methods is essential. Among the viable alternatives, hydroponic fertilizer (HF) emerges as a widely available option, particularly in regions such as Indonesia. Typically, HF is supplied in two distinct forms, powdered Mix-A and Mix-B, to prepare the stock solutions. This study investigates the impact of varying concentrations and stock solution ratios on both the growth rate and biomass yield of C. vulgaris. Additionally, an economic analysis of cultivation activities is conducted, with a specific focus on comparing the feasibility of utilizing hydroponic fertilizer against conventional methods. The findings reveal that specific ratios and concentrations of the tested growth media outperform standard media in promoting the growth rate and biomass yield of cultivated C. vulgaris. Furthermore, the economic analysis assesses two primary cost components: fertilizer and energy. All tested hydroponic media offered a more cost-effective cultivation solution compared to conventional methods, primarily attributed to the lower cost of the hydroponic fertilizers.

Overexpression of native carbonic anhydrases increases carbon conversion efficiency in the methanotrophic biocatalyst Methylococcus capsulatus Bath.

Methanotrophic bacteria play a vital role in the biogeochemical carbon cycle due to their unique ability to use CH4 as a carbon and energy source. Evidence suggests that some methanotrophs, including Methylococcus capsulatus, can also use CO2 as a carbon source, making these bacteria promising candidates for developing biotechnologies targeting greenhouse gas capture and mitigation. However, a deeper understanding of the dual CH4 and CO2 metabolism is needed to guide methanotroph strain improvements and realize their industrial utility. In this study, we show that M. capsulatus expresses five carbonic anhydrase (CA) isoforms, one α-CA, one γ-CA, and three β-CAs, that play a role in its inorganic carbon metabolism and CO2-dependent growth. The CA isoforms are differentially expressed, and transcription of all isoform genes is induced in response to CO2 limitation. CA null mutant strains exhibited markedly impaired growth compared to an isogenic wild-type control, suggesting that the CA isoforms have independent, non-redundant roles in M. capsulatus metabolism and physiology. Overexpression of some, but not all, CA isoforms improved bacterial growth kinetics and decreased CO2 evolution from CH4-consuming cultures. Notably, we developed an engineered methanotrophic biocatalyst overexpressing the native α-CA and β-CA with a 2.5-fold improvement in the conversion of CH4 to biomass. Given that product yield is a significant cost driver of methanotroph-based bioprocesses, the engineered strain developed here could improve the economics of CH4 biocatalysis, including the production of single-cell protein from natural gas or anaerobic digestion-derived biogas.IMPORTANCEMethanotrophs transform CH4 into CO2 and multi-carbon compounds, so they play a critical role in the global carbon cycle and are of interest for biotechnology applications. Some methanotrophs, including Methylococcus capsulatus, can also use CO2 as a carbon source, but this dual one-carbon metabolism is incompletely understood. In this study, we show that M. capsulatus carbonic anhydrases are critical for this bacterium to optimally utilize CO2. We developed an engineered strain with improved CO2 utilization capacity that increased the overall carbon conversion to cell biomass. The improvements to methanotroph-based product yields observed here are expected to reduce costs associated with CH4 conversion bioprocesses.

Microbial production of food compounds with carbon dioxide and derived low-carbon molecules as substrates

The construction and optimization of microbial cell factories are crucial steps and key technologies in achieving green biomanufacturing. As concern has been aroused regarding the excessive carbon dioxide (CO2) emissions and food security, a new and promising research field, microbial conversion of CO2 into food compounds, has emerged. The research in this field not only holds significant implications for achieving the carbon peaking and carbon neutrality goals but also plays a role in maintaining food security. This paper provides a comprehensive review and outlook of the research on utilizing CO2 and its derived low-carbon chemicals for the production of food compounds, focusing on the production of glucose, sugar derivatives, and single-cell proteins and the development of artificial CO2 fixation pathways.

Production of Single Cell Protein (SCP) from the Peel Waste of Pea, Potato, and Banana by Aspergillus Flavus NRRL 21882 as an Efficient Organic Poultry Supplement.

Food protein deficit has become a major issue worldwide, particularly in underdeveloped countries. Scientists are searching for a variety of less expensive solutions to this issue. One of these less expensive methods is to create single cell protein as a substrate from leftover fruit and vegetable waste, which is typically thrown away. In this regard, the fungal strain Aspergillus flavus (NRRL 21882) was used for the synthesis of SCP (single cell protein) from the waste of banana, potato, and pea. In this manner, 30 samples were collected from the whole substrate with a share of 10 samples each from banana, potato, and pea peels, which were in turn dried and powdered finely. The fermentation process was done by the process of solid state fermentation. Aspergillus flavus (NRRL 21882) generated the highest percentage, i.e. 60.67%, of crude protein from the pea peels. The composition of amino acids in crude proteins was also investigated. The findings demonstrated that the highest percentage of aspartic acid (13.34 ± 0.80%) and glutamic acid (14.92 ± 0.69%) was found in A. flavus single cell protein produced from pea peels. Soybean was supplemented with single cell protein in the boilers' diet. Compared to all treated groups, there was a substantial (p ≤ 0.05) increase in the level of antibody titer against the Newcastle disease vaccine. The supplementation of single cell protein with soybean meal had no effect on the levels of liver enzymes. The liver enzymes found in all four groups (A, B, C, and D) were within normal limits. None of the examined groups experienced any change in the feed conversion ratio, with all groups exhibiting an average FCR of 1.6. The current study concludes that broiler health and immunity is increased by supplementing poultry feed with single cell protein.

Resource recovery and treatment of wastewaters using filamentous fungi

Industrial wastewater, often characterized by its proximity to neutral pH, presents a promising opportunity for fungal utilization despite the prevalent preference of fungi for acidic conditions. This review addresses this discrepancy, highlighting the potential of certain industrial wastewaters, particularly those with low pH levels, for fungal biorefinery. Additionally, the economic implications of biomass recovery and compound separation, factors that require explicit were emphasized. Through an in-depth analysis of various industrial sectors, including food processing, textiles, pharmaceuticals, and paper-pulp, this study explores how filamentous fungi can effectively harness the nutrient-rich content of wastewaters to produce valuable resources. The pivotal role of ligninolytic enzymes synthesized by fungi in wastewater purification is examined, as well as their ability to absorb metal contaminants. Furthermore, the diverse benefits of fungal biorefinery are underscored, including the production of protein-rich single-cell protein, biolipids, enzymes, and organic acids, which not only enhance environmental sustainability but also foster economic growth. Finally, the challenges associated with scaling up fungal biorefinery processes for wastewater treatment are critically evaluated, providing valuable insights for future research and industrial implementation. This comprehensive analysis aims to elucidate the potential of fungal biorefinery in addressing industrial wastewater challenges while promoting sustainable resource utilization.

Conditional Optimization of Single Cell Protein Production from Crude Oil by <i>Pseudomonas aeruginosa</i>

The study was carried out to investigate the possible biodegradation of crude oil as a carbon by the bacterium <i>Pseudomonas aeruginosa</i> isolated from marine environment (Ras El-Menkar- Benghazi- Libya) using basal yeast extract protease peptone-3 (BYP) enriched medium. The isolated bacterium was identified and characterized according to its cultural condition and microbial biochemical properties. Different experiments were developed throughout this study to stimulate bacterial growth and production of single cell protein (SCP). The results show that the optimal concentration of crude oil as a carbon source for the highest bacterial growth (1.14g/l), and production of SCP (0.65g/l; 57.02% of the biomass dry weight) was 1%. This was required to utilize up to 50.6% of oil as a carbon source. As to the nitrogen source, the optimal concentration of ammonium chloride was 0.1%, in which the bacterial growth and SCP production increased to 1.23 g/l and 0.67 g/l respectively. The stimulating effects of organic and inorganic factors on the bacterial growth and SCP production was also tested. Addition of inorganic nutrients such as potassium phosphate (0.05%), magnesium sulphate (0.01%), and organic nutrient in the form of yeast extract (0.1%) to the fermentation medium slightly promoted the bacterial growth which reflected positively on SCP production and the percentage of the consumed crude oil, (>57%) at final pH value of 8.0. The obtained results indicated that the isolated<i> Pseudomonas aeruginosa</i> posses the ability to utilize the crude oil and use it as a carbon for bacterial growth and production of SCP.

Enhancing Protein Content in Wild-Type Saccharomyces cerevisiae via Random Mutagenesis and Optimized Fermentation Conditions.

Single-cell protein (SCP) derived from microorganisms is widely recognized as a viable alternative protein source for the future. Nevertheless, the commercialization of yeast-based SCP is hampered by its relatively low protein content. Therefore, this study aimed to enhance the protein content of Saccharomyces cerevisiae via random mutagenesis. To achieve this, S. cerevisiae KCCM 51811, which exhibited the highest protein concentration among 20 edible S. cerevisiae strains, was selected as a chassis strain. Subsequently, a KCCM 51811 mutant library was constructed (through UV irradiation) and screened to isolate mutants exhibiting high protein content and/or concentration. Among the 174 mutant strains studied, the #126 mutant exhibited a remarkable 43% and 36% higher protein content and concentration, respectively, compared to the parental strain. Finally, the #126 mutant was cultured in a fed-batch system using molasses and corn-steep liquor, resulting in a protein concentration of 21.6 g/l in 100 h, which was 18% higher than that produced by the parental strain. These findings underscore the potential of our approach for the cost-effective production of food-grade SCP.

Optimizing cultural conditions and pretreatment for high-value single-cell protein from vegetable waste

The study aimed to produce single-cell protein (SCP) from vegetable waste through solid-state fermentation (SSF) using tomato, capsicum, eggplant, and cucumber waste. Three yeast strains, namely Candida tropicalis, Candida krusei, and Saccharomyces cerevisiae were selected to optimize cultural conditions without pretreatment of the substrate to obtain a higher yield of SCP. The study identified the best-performing yeast strains and optimized the acid and thermal hydrolysis pretreatment of vegetable waste using central composite design by response surface methodology. The substrate was pretreated with varying concentrations of sulfuric acid (2 %, 4 %, and 6 % w/v) at temperatures of 120°C, 140°C, and 160°C. The study demonstrated that SCP production could be enhanced with the acid and thermal hydrolysis of nutrient-supplemented vegetable waste by using optimized cultural conditions. Without pretreatment of vegetable waste, the yeast combination of Saccharomyces cerevisiae and Candida tropicalis achieved a maximum protein content of 10.8 mg/g of dry biomass (an increment of 63.6 % compared to control). With the same yeast strains, pretreatment of vegetable waste (with 4 % sulfuric acid at 140°C) and supplemented with a nutrient source increased SCP production to 21.9 and 31.7 mg/g (an increment of 231.8 % and 375.8 % compared to control), respectively. The study's findings suggest that SCP production from vegetable waste can be optimized through SSF and acid-thermal hydrolysis pretreatment, which could be a promising approach for efficient waste management.

Single-Cell Protein and Ethanol Production of a Newly Isolated Kluyveromyces marxianus Strain through Cheese Whey Valorization.

The present work examined the production of single-cell protein (SCP) by a newly isolated strain of Kluyveromyces marxianus EXF-5288 under increased lactose concentration of deproteinized cheese whey (DCW) and different temperatures (in °C: 20.0, 25.0, 30.0 and 35.0). To the best of the authors' knowledge, this is the first report examining the ability of Kluyveromyces marxianus species to produce SCP at T = 20.0 °C. Different culture temperatures led to significant differences in the strain's growth, while maximum biomass and SCP production (14.24 ± 0.70 and 6.14 ± 0.66 g/L, respectively) were observed in the cultivation of K. marxianus strain EXF-5288 in shake-flask cultures at T = 20.0 °C. Increased DCW lactose concentrations (35.0-100.0 g/L) led to increased ethanol production (Ethmax = 35.5 ± 0.2 g/L), suggesting that K. marxianus strain EXF-5288 is "Crabtree-positive". Batch-bioreactor trials shifted the strain's metabolism to alcoholic fermentation, favoring ethanol production. Surprisingly, K. marxianus strain EXF-5288 was able to catabolize the produced ethanol under limited carbon presence in the medium. The dominant amino acids in SCP were glutamate (15.5 mg/g), aspartic acid (12.0 mg/g) and valine (9.5 mg/g), representing a balanced nutritional profile.

Valorisation of industrial hemp (Cannabis sativa L.) residues and cheese whey into volatile fatty acids for single cell protein production

The production of single cell protein (SCP) using lignocellulosic materials stands out as a promising route in the circular bioeconomy transition. However, multiple steps are necessary for lignocellulosics-to-SCP processes, involving chemical pretreatments and specific aerobic cultures. Whereas there are no studies that investigated the SCP production from lignocellulosics by using only biological processes and microbial biomass able to work both anaerobically and aerobically. In this view, the valorisation of industrial hemp (Cannabis sativa L.) biomass residues (HBRs), specifically hurds and a mix of leaves and inflorescences, combined with cheese whey (CW) was investigated through a semi-continuous acidogenic co-fermentation process (co-AF). The aim of this study was to maximise HBRs conversion into VFAs to be further used as carbon-rich substrates for SCP production. Different process conditions were tested by either removing CW or increasing the amount of HBRs in terms of VS (i.e., two and four times) to evaluate the performance of the co-AF process. Increasing HBRs resulted in a proportional increase in VFA production up to 3115 mg HAc L−1, with experimental production nearly 40% higher than theoretical predictions. The synergy between HBRs and CW was demonstrated, proving the latter as essential to improve the biodegradability of the former. The produced VFAs were subsequently tested as substrates for SCP synthesis in batch aerobic tests. A biomass concentration of 2.43 g TSS L−1 was achieved with a C/N ratio of 5.0 and a pH of 9.0 after two days of aerobic fermentation, reaching a protein content of 42% (g protein per g TSS). These results demonstrate the overall feasibility of the VFA-mediated HBR-to-SCP valorisation process.

Bioelectrochemical protein production valorising NH3-rich pig manure-derived wastewater and CO2 from anaerobic digestion

Microbial electrosynthesis (MES) cell use is an innovative approach for single-cell proteins (SCP) production. Coupling MES with the valorization of CO2 from anaerobic digestion and nitrogen from livestock effluents has beneficial environmental effects, reducing greenhouse gas emissions and nitrogen overloading. In addition, the reducing power needed can come from surplus renewable energy. In this study, MES with a biochar-functionalized cathode was tested at varying polarizations, i.e. non polarized, −0.6 V and −1.0 V vs Ag/AgCl, and biogas-derived CO2 and recovered ammonia from pig slurry was supplied.Negative polarization switched the microbial community from heterotrophic, typical of unpolarized MES, to a mix of both heterotrophic and autotrophic/electrotrophic communities at −0.6 V and to mainly autotrophic/electrotrophic at −1.0 V. The more negative polarization allowed the highest CO2 and N capture, i.e. 39 ± 2 % of the supplied CO2, and 6.7 ± 0.8 % supplied N. Microbial biomass characterization indicated a protein content on dry matter basis of 33.1 ± 1.3 % (unpolarized), 43.2 ± 0.6 % (−0.6 V) and 69.1 ± 1.0 % (−1.0 V). The amino acids profiles investigated showed a high nutritional value of the produced biomass, not far from those of conventional protein sources used for producing feed/food.

Enhanced productivity of nutrient-rich single cell protein from Paradendryphiella arenariae PG1 through valorization of agro-industrial waste: A Green symphony from Waste-to-Protein Approach

The rise in global population strains agro-industrial waste management, positioning single-cell protein (SCP) production as a cost-effective solution. Evaluating eight agro-waste residues identified wheat bran with a high solid recovery rate (67.15 %). SCP production increased from 1.29 ± 0.23 gL−1 to 21.05 ± 0.33 gL−1, achieving a microbial conversion efficiency of 90.88 % by Paradendryphiella arenariae (PG1). Nucleic acid content in SCP was reduced by 31 % using NaOH and 36 % via heat shock, significantly enhancing SCP quality, digestibility, and safety. SCP's impact on Caenorhabditis elegans (C. elegans) revealed a maximum lifespan of 18 ± 0.2 days, notable pharyngeal pumping rates (117 ± 2.541 and 67 ± 3.473 min−1 on days 5 and 10), and body bending rates (115.3 ± 0.86 and 44.8 ± 0.28 min−1 on days 5 and 10). This comprehensive approach demonstrates the promise of SCP production in sustainable waste management, resource optimization, and detailed toxicity analysis in C. elegans, broadening the potential applications of SCP in various fields.

Creation of Single Cell Protein-Producing Mutants of Phaffia Rhodozyma

Recently, there has been an increasing demand for sustainable protein sources for aquaculture. In aquaculture, sustainable protein includes sources that can be produced with a minimal environmental footprint, such as single-cell proteins, proteins from algae, insects, and by-products from the agricultural industry. Single-cell proteins that are derived from microorganisms show a sustainable alternative to traditional protein sources due to their high protein content and rapid growth. This research focuses on creating mutants of the yeast Phaffia rhodozyma to increase single-cell protein production. This yeast has significant industrial potential and biological features. The yeast Phaffia rhodozyma is already known for its unique ability to synthesize astaxanthin, so this case will focus on its ability to produce protein. In the study, we used wild strain yeast and previously obtained white mutants on inorganic nitrogen media for further random mutagenesis methods to introduce specific mutations into the genome aimed at improving their ability to biosynthesize protein. Amino acid inhibitor was used to select potential protein-producing mutants. The protein content of the biomass obtained from the experiments was analyzed in detail using BCA (Protein Assay Reagent) analysis, which confirmed their potential as a source of nutrients for aquaculture. This method is based on the reaction between bicinchoninic acid and the peptide bonds of proteins, which results in the formation of a color whose intensity is proportional to the amount of protein in the sample. The results obtained allow further research into the development of cost-effective and environmentally friendly alternatives for feed in aquaculture.

Single cell protein production from methane in a gas-delivery membrane bioreactor

Single cell protein (SCP, or microbial protein) is one of the emerging alternative protein sources to address the global challenge of food insecurity. Recently, the SCP produced from methane has attracted substantial attention since methane is a renewable resource attainable from anaerobic digestion. However, the supply of methane, an insoluble gas in water, is one of the major challenges in producing methane-based SCP. This work developed a novel bioreactor configuration, in which hollow fiber membrane was used for efficient methane supply while microorganisms were growing in the suspended form favourable for the biomass harvest. Over a 312-day operation, the impacts of three critical parameters on the SCP production were investigated, including the ratio of methane loading to ammonium loading, the ratio of methane loading to oxygen loading, and the sludge retention time (SRT). Under the condition of 4 g CH4/g NH4+, 4 g O2/g CH4, and SRT of 4 days, the highest SCP production yield was observed and determined to be 1.36 g SCP/g CH4 and 5.05 g SCP/g N, respectively. The protein content was up to 67 %, which is higher than the majority of reported values to date. Moreover, the methane and ammonium utilization efficiencies were both close to 100 %, suggesting the highly efficient utilization of substrates in this new bioreactor configuration. A high relative abundance of essential amino acids (EAA) above 42 % was achieved, representing the highest EAA content reported. These findings provide valuable insights into SCP production using methane as a feedstock.