Single Cell Protein Production Research Articles

Homologous High-Level Lipase and Single-Cell Protein Production with Engineered Yarrowia lipolytica via Scale-Up Fermentation for Industrial Applications

Yarrowia lipolytica is a promising feed additives. Here, we aimed to produce extracellular lipases and single-cell proteins (SCPs) at high levels simultaneously through fed-batch fermentation of engineered Y. lipolytica. The parameters for 500 mL shake flask cultures were optimized with a single factorial design. The resultant activity of lipase reached 880.6 U/mL after 84 h of fermentation, and 32.0 g/L fermentation broth of dry SCP was obtained at 120 h. To attain high SCP and lipase productivity, the high-density fed-batch fermentation of Y. lipolytica was scaled up in 10 L, 30 L, and 100 L fermentors. Using glycerol as the sole carbon source, the lipase activity peaked to 8083.3 U/mL, and the final dry SCP weight was 183.1 g/L at 94.6 h in 10 L fermentors. The extracellular lipase activity and SCP weight reached 11,100.0 U/mL and 173.3 g of dry SCP/L at 136 h in 30 L fermentors, respectively. Following 136 h of fed-batch fermentation, the extracellular lipase activity and dry SCP weight reached 8532.0 U/mL and 170.3 g/L in 100 L fermentors, respectively. A balance between the lipase secretion and growth of Y. lipolytica recombinant strain was achieved, indicating that an efficient fermentation strategy could promote further scale-up for industrial SCP production from engineered Y. lipolytica.

Microbial conversion of waste gases into single-cell protein

Climate change and food security are two of our most significant global challenges of our time. Conventional approaches for food production not only produce greenhouse gases but also require extensive land and water resources. An alternative is to use gas fermentation to convert greenhouse gases as feedstocks into microbial protein-rich biomass (single-cell protein). Aerobic methanotrophic (methane-oxidising) and hydrogenotrophic (hydrogen-oxidising) bacteria, which produce biomass using gases as their energy and carbon sources, are ideal candidates for single-cell protein production. However, multiple innovations are required for single-cell protein production to be economical and sustainable. Although current technologies rely on conversion of purified single gaseous substrates, the potential to directly use mixed gas streams from point sources remains reasonably unexplored. In addition, there is much potential to increase nutritional and commercial value of single-cell protein through synthetic biology. In this perspective, we discuss the principles, approaches, and outlook for gas fermentation technologies aiming to significantly reduce greenhouse gas emissions and enhance food security.

Effect of pH and Different Fermentation Time Intervals on the Production of Single Cell Proteins (SCPs) from Potato Peels

Dried cells of microorganisms such as fungi, algae, and bacteria, known as Single-Cell Proteins (SCPs), are utilized as a source of protein supplements in animal feed or human food. These SCPs can be produced through the use of low-cost feedstocks and waste materials as sources of carbon and energy, which can be converted into biomass and concentrated proteins. Objective: To optimize the yield and growth of dry cell biomass through the manipulation of fermentation conditions. Methods: A batch fermentation process was used to produce dry cell biomass from a microorganism. Different pH values, fermentation times, and reactor configurations were tested, and the resulting biomass was analyzed for its protein content. Results: The maximum yield of dry cell biomass was achieved at pH 4.5, with a yield of 1.951 g/100 ml. The maximum dry biomass was achieved after 72 hours of fermentation, with a yield of 2.824 g/100 ml. The maximum yield of dry biomass was achieved with an Airlift fermenter at an aeration rate of 1.0 vvm and a temperature of 35°C for 72 hours, resulting in a yield of 5.452 g/L. The protein content of the dried cell biomass was found to be in the range of 45-55%. Conclusions: This study demonstrates that the yield and growth of dry cell biomass can be optimized by controlling the fermentation conditions, specifically pH, fermentation time, and reactor configuration. These findings may have implications for the industrial-scale production of dry cell biomass, as they offer insight into how to maximize yield and protein content.

Sugar Beet Pulp as a Biorefinery Substrate for Designing Feed.

An example of the implementation of the principles of the circular economy is the use of sugar beet pulp as animal feed. Here, we investigate the possible use of yeast strains to enrich waste biomass in single-cell protein (SCP). The strains were evaluated for yeast growth (pour plate method), protein increment (Kjeldahl method), assimilation of free amino nitrogen (FAN), and reduction of crude fiber content. All the tested strains were able to grow on hydrolyzed sugar beet pulp-based medium. The greatest increases in protein content were observed for Candida utilis LOCK0021 and Saccharomyces cerevisiae Ethanol Red (ΔN = 2.33%) on fresh sugar beet pulp, and for Scheffersomyces stipitis NCYC1541 (ΔN = 3.04%) on dried sugar beet pulp. All the strains assimilated FAN from the culture medium. The largest reductions in the crude fiber content of the biomass were recorded for Saccharomyces cerevisiae Ethanol Red (Δ = 10.89%) on fresh sugar beet pulp and Candida utilis LOCK0021 (Δ = 15.05%) on dried sugar beet pulp. The results show that sugar beet pulp provides an excellent matrix for SCP and feed production.

Life-cycle assessment of yeast-based single-cell protein production with oat processing side-stream

Production of fish meal and plant-based feed proteins continues to increase to meet the growing demand for seafood, leading to impacts on marine and terrestrial ecosystems. Microbial proteins such as single-cell proteins (SCPs) have been introduced as feed alternatives since they can replace current fish feed ingredients, e.g., soybean, which are associated with negative environmental impacts. Microbial protein production also enables utilization of grain processing side-streams as feedstock sources. This study assesses the environmental impacts of yeast-based SCP using oat side-stream as feedstock (OS-SCP). Life-cycle assessment with a cradle-to-gate approach was used to quantify global warming, freshwater eutrophication, marine eutrophication, terrestrial acidification, land use, and water consumption of OS-SCP production in Finland. Dried and wet side-streams of oat were compared with each other to identify differences in energy consumption and transportation effects. Sensitivity analysis was performed to examine the difference in impacts at various locations and fermentation times. Benchmarking was used to evaluate the environmental impacts of OS-SCP and other feed products, including both conventional and novel protein products. Results highlight the importance of energy sources in quantifying the environmental performance of OS-SCP production. OS-SCP produced with dried side-streams resulted in higher global warming (16.3 %) and water consumption (7.5 %) than OS-SCP produced from wet side-streams, reflecting the energy and water requirements for the drying process. Compared with conventional products, such as soy protein concentrates, OS-SCP resulted in 61 % less land use, while exacerbating the environmental impacts in all the other categories. OS-SCP had more impact on global warming (205–754 %), water consumption (166–1401 %), freshwater eutrophication (118–333 %), and terrestrial acidification (85–340 %) than other novel products, including yeast protein concentrate, methanotrophic bacterial SCP, and insect meal, while lowering global warming (11 %) and freshwater eutrophication (20 %) compared with dry microalgae biomass.

Microbial community-based production of single cell protein from soybean-processing wastewater of variable chemical composition

The use of food-processing wastewaters to produce microbial biomass-derived single cell protein (SCP) is a sustainable way to meet the global food demand. Microbial community-based approaches to SCP production have the potential benefits of lower costs and greater resource recovery compared to pure cultures, yet they have received scarce attention. Here, SCP production from soybean-processing wastewaters using their existent microbial communities was evaluated. Six sequencing batch reactors of 4.5-L working volume were operated at 30 °C for 34 d in cycles consisting of 3-h anaerobic and 9-h aerobic phases. Four reactors received no microbial inoculum and the remaining two were amended with 1.5 L of a mixed culture from a prior SCP production cycle. Reactors produced more SCP when fed with wastewaters of higher soluble total Kjeldahl nitrogen (sTKN) content. The protein yield in biomass ranged from 0.53 to 3.13 g protein/g sTKN, with a maximum protein content of 50 %. The average removal of soluble chemical oxygen demand (sCOD) and soluble total nitrogen (sTN) was 92 % and 73 %, respectively. Distinct microbial genera were enriched in all six bioreactors, with Azospirillum, Rhodobacter, Lactococcus, and Novosphingobium dominating. The study showed that constituents in soybean wastewater can be converted to SCP and demonstrated the effect of variable influent wastewater composition on SCP production.

Amino acid profile and protein bioaccessibility of two Galdieria sulphuraria strains cultivated autotrophically and mixotrophically in pilot-scale photobioreactors

Galdieria sulphuraria is considered one of the most promising microalgae for food applications. In this study, we compared two strains of G. sulphuraria cultivated autotrophically and mixotrophically over 35 days in pilot-scale photobioreactors under nonsterile conditions. The low pH (<1.9) used for cultivation successfully prevented microbial contamination. The two strains had similar autotrophic and mixotrophic biomass productivities, the latter being 2.3 times higher than autotrophic productivity. Comparing the two strains, G. sulphuraria SAG 108.79 and ACUF 064 had 51% and 64% (w/w) protein and 4% and 9% (w/w) C-phycocyanin content, respectively. Interestingly, G. sulphuraria SAG 108.79 showed a protein bioaccessibility of 62%, in line with other microalgal species, whereas G. sulphuraria ACUF 064 had a protein bioaccessibility of only 14%. No differences in the amino acid profile were found between the two strains or between trophic modes. Stable and well-balanced protein profiles are encouraging results for future applications of this species. Industrial relevanceThe main focus of this study was the production of single-cell proteins using two strains of the polyextremophilic microalgae Galdieria sulphuraria. The acidic cultivation condition was sufficient to guarantee axenic production in not sterile conditions, even in the presence of glucose. Both strains were rich in proteins with a similar amino acid profile rich in all of the essential amino acids. Interestingly, there was a 4.4-fold difference in protein bioaccessibility between the two strains. Simple production of axenic microalgal biomass rich in protein is an encouraging result for future food applications of this species.

Agricultural wastes for brine shrimp Artemia production: A review

AbstractAn increasing global population has meant aquaculture, one of the fastest growing food industry sectors, faces significant sustainability challenges as it tries to address the rising global protein demand. In many sectors, production is underpinned by fishmeal as dietary ingredient, but this is a finite resource with competing users from the poultry and livestock industries. Alternatively, some (planktonic) aquatic species, especially brine shrimp Artemia, can be produced using agricultural waste to provide food or biomass to support increasing aquaculture demand. This review investigates research and production of Artemia using agricultural waste. Various systems used for Artemia production in inoculated ponds are analysed and discussed to provide options for environmentally sustainable food systems that can be applied from either an artisanal level in developing countries with a considerable labour force, or in intensive systems in countries with large volumes of under‐utilised resources, for example, sugar/alcohol‐based waste and inland saline areas. Using agricultural waste, single cell protein production in a separate aerobic digester can be a simple, continuous food source for Artemia to enable daily biomass harvest. This could then be used as a fishmeal replacement or possibly for human consumption to promote a circular economy by remediating waste to produce protein, like a food production mine.

Sustainable production of single-cell oil and protein from wastepaper hydrolysate: identification and optimization of a Rhodotorula mucilaginosa strain as a promising yeast.

This study investigated the potential of wastepaper hydrolysate as a sustainable and low-cost carbon source for single-cell oil and protein production, attending to the growing need for alternative feedstocks and waste management strategies. Wastepaper, characterized by its high carbohydrate content, was subjected to enzymatic and chemo-enzymatic treatments for carbohydrate release. The chemo-enzymatic treatment performed better, yielding 65.3g l-1 of fermentable sugars. A total of 62 yeast strains were screened for single-cell oil accumulation, identifying Rhodotorula mucilaginosa M1K4 as the most advantageous oleaginous yeast. M1K4 lipid production was optimized in liquid culture, and its fatty acid profile was analyzed, showing a high content of industrially valuable fatty acids, particularly palmitic (28%) and oleic (51%). Batch-culture of M1K4 in a 3-l reactor demonstrated the strain's ability to utilize wastepaper hydrolysate as a carbon source, with dry cell weight, total lipid and protein production of 17.7g l-1, 4.5g l-1, and 2.1g l-1, respectively. Wastepaper as a substrate provides a sustainable solution for waste management and bioproduction. This research highlights the potential of R. mucilaginosa for lipid and protein production from wastepaper hydrolysate.

Single-cell protein production by Pleurotus ostreatus in submerged fermentation

P. ostreatus biomass could stand as an alternative vegan protein source due to its high protein content and amino acid composition.

Isolation and biochemical characterization of natural algal isolates from Kangsabati River, West Bengal toward single-cell proteins production

Isolation and biochemical characterization of natural algal isolates from Kangsabati River, West Bengal toward single-cell proteins production

Production of Single Cell Protein from Banana Peel, Papaya Juice and Whey and Estimation of Protein Concentration

Objectives: This study was aimed to produce single cell protein from possible substrate to yield high protein concentration. Methods: All three types of samples viz banana peel, papaya juice and whey were examined for the estimation of protein concentration. The study was carried out in the Microbiological Laboratory of the Department of Microbiology, D.A.V. College, Dhobighat, Lalitpur from October 19, 2019 to November 29, 2019. The fermentation process was carried out at 32℃ for 5 days and physiochemical analysis of medium was performed every 24 hours. After fermentation, the microbial biomass was extracted and protein concentration was estimated colorimetrically by modified Biuret method. Results: Out of three samples, papaya juice had the highest yeast cell count of 136.25×104 cells/ml followed by whey extract producing 124×104 cells/ml and, the least cell was by banana peel of 104×104 cells/ml. The protein concentration was estimated by the modified biuret’s test. The SCP produced from papaya juice was highest with protein concentration of 23.5% followed by whey extract of 22% and, the lowest protein concentration was of SCP produced from banana peel with 16.04%. Conclusion: The result of this study suggests that production of SCP from whey extract is considered best in terms of better yield and low cost.

Isolation and Characterization of Yeasts from Locally Available Foods

A study was conducted to identify different isolates of yeasts which are prospective to be utilized in various industries from locally available foods. Altogether 24 yeast isolates were obtained from fermented fruits and vegetables (banana, cabbage, grapes, lime and mango), pudding, bee honey, toddy and fermented fish samples using the pour plate method. Characterization of the yeasts using several biochemical tests (urease, catalase, liquid carbon and nitrogen assimilation and sugar fermentation tests) revealed that this pool was composed with yeast strains belong to genera of Saccharomyces, Kluvyeromyces, Candida, Pseudozyma, Cryptococcus, Rhodotorula and Debaryomyces. The most effective lactose fermenters were identified as viable candidates for bioethanol production and for manufacturing fermented dairy products for lactose intolerant people. Yeasts with the highest biomass production were suggested as the best viable candidates for industrial single cell protein production using whey, the major byproduct of the dairy industry. The five thermo-tolerant yeasts (Y55, Y57, Y58, Y59 and Y70) and Y069 which was optimally active under 10C were recognized as suitable for industrial applications. The isolates tolerant for high osmotic pressure conditions were identified as potential isolates to be used in highly concentrated food products. Sugarcane juice was recognized as a possible medium for the cultivation of these yeasts in industrial settings. The beneficial yeasts forecasting in this study are expected to screen using molecular biological methods to utilize them in industrial applications.

Biotechnological Production of Sustainable Microbial Proteins from Agro-Industrial Residues and By-Products.

Microbial proteins, i.e., single-cell proteins or microbial biomass, can be cultivated for food and animal feed due to their high protein content and the fact that they represent a rich source of carbohydrates, minerals, fats, vitamins, and amino acids. Another advantage of single-cell proteins is their rapid production due to the growth rate of microorganisms and the possibility of using agro-industrial waste, residues and by-products for production through this renewable technology. Agro-industrial residues and by-products represent materials obtained from various processes in agriculture and agriculture-related industries; taking into account their composition and characteristics, as well as vast amounts, they have an enormous potential to generate sustainable bioproducts, such as microbial proteins. This review aims to summarize contemporary scientific research related to the production of microbial proteins on various agro-industrial residues and by-products, as well as to emphasize the current state of production of single-cell proteins and the importance of their production to ease the food crisis and support sustainable development.

High-yield production of single-cell protein from starch processing wastewater using co-cultivation of yeasts

Single-cell protein (SCP) from potato starch processing wastewater (PSPW) shows great potential against protein scarcity and unsustainable production of plant and animal proteins. In this study, five yeasts were selected to conduct a series of PSPW fermentation for obtaining high-value SCP by optimizing fermentation conditions. The yeast combination was optimized as Candida utilis, Geotrichum candidum and Candida tropicalis with the volume proportion of 9:5:1. The inoculum size, temperature, rotation speed and initial pH were optimized at 12 %, 24℃, 200 r·min−1 and ∼ 4.13 (natural pH), respectively. At the optimal conditions, SCP yield of 3.06 g·L−1 and water-soluble protein of 17.32 % were obtained with the chemical oxygen demand removal of 56.9 %. A resource-recycling process of PSPW was proposed by coupling yeast fermentation and up-flow anaerobic sludge blanket (UASB) treatment to achieve simultaneous high-level organic removal and SCP production, which could be a promising alternative technology for PSPW treatment.

Recent Advances and Technologies in Chitinase Production Under Solid-State Fermentation

ABSTRACT: Our target is to evaluate recent literature on chitinase production from different sources via solid-state fermentation and to analyze several strategies to improve chitinase production via solid-state fermentation. Plant pathogen biocontrol, sequential transformation of chitin into bioactive molecules such as chito-oligosaccharides and N-acetylglucosamine, protoplast synthesis from filamentous fungi, and single-cell protein production are some of the applications for chitinase. Despite their enormous biological importance, chitinases have received little commercial importance due to the smaller percentage of microbes with high efficiencies, the enzymes' decreased activity and consistency, and the cost of production. Solid-state fermentation (SSF) is less expensive, requires fewer vessels, uses less water, requires fewer wastewater treatments, produces a greater product yield, has a lower risk of bacterial contamination, and requires less energy expenditure. Despite its higher productivity and lower cost, the SSF technique is now mostly limited to lab scales. Furthermore, the crude SSF products can be used as an enzyme source for biotransformation. There are many findings on different microorganisms that produce chitinase by SSF. So it is very critical to isolate new organisms for such production. So we assessed the traditional approach to medium optimization, which focuses on changing one factor at a time while leaving the others constant, and statistical optimization techniques such as response surface methodology (RSM), artificial neural networks (ANNs), and genetic algorithms (GA).

Effect of nutrients deficiency on biofilm formation and single cell protein production with a purple non-sulphur bacteria enriched culture

Purple non-sulphur bacteria (PNSB) are of interest for biorefinery applications to create biomolecules, but their production cost is expensive due to substrate and biomass separation costs. This research has utilized fuel synthesis wastewater (FSW) as a low-cost carbon-rich substrate to produce single-cell protein (SCP) and examines PNSB biofilm formation using this substrate to achieve a more efficient biomass-liquid separation. In this study, PNSB were grown in Ca, Mg, S, P, and N-deficient media using green shade as biofilm support material. Among these nutrient conditions, only N-deficient and control (nutrient-sufficient) conditions showed biofilm formation. Although total biomass growth of the control was 1.5 times that of the N-deficient condition and highest overall, the total biofilm-biomass in the N-deficient condition was 2.5 times greater than the control, comprising 49% of total biomass produced. Total protein content was similar between these four biomass samples, ranging from 35.0 ± 0.2% to 37.2 ± 0.0%. The highest protein content of 44.7 ± 1.3% occurred in the Mg-deficient condition (suspended biomass only) but suffered from a low growth rate. Overall, nutrient sufficient conditions are optimal for overall protein productivity and dominated by suspended growth, but where fixed growth systems are desired for cost-effective harvesting, N-deficient conditions provide an effective means to maximize biofilm production without sacrificing protein content.

Potential of Single Cell Protein Production Using Waste as Growth Medium

Feed is an important factor affecting the growth of cultured fish. Around 86.5% of the production cost of aquaculture is allocated for the purchase of feed. Good quality and efficient feed is a determinant of the success of aquaculture business. Single Cell Protein (SCP) is a dry cell product of single cell microorganisms. SCP production is generally not only protein but also free amino acids, lipids, carbohydrates, vitamins and minerals. The purpose of this study was to analyze the growth media of Bacillus Cereus which will be used as a source of SCP by using some easy-to-use waste. The research method used is an experimental method using 2 isolates of Bacillus cereus bacteria, namely B. cereus strain SN7 and a consortium of bacterial isolates. Both isolates were grown in tofu liquid waste media, sago liquid waste media, and molasses waste media as a carbon source added with egg white as a nitrogen source with 3 replications in each treatment. The results showed that the most optimal growth medium for B. cereus strain SN7 and the consortium was molasses waste modified media which was incubated for 24 hours, compared to modified media for sago waste and tofu waste. For comparison, the isolates of B. cereus and consortium still had a higher growth potential than the isolates of strain SN7 which had been incubated for 24 hours.

Ammonia nitrogen recovery from biogas slurry by SCP production using Candida utilis

The safe and robust yeast Candida utilis was employed for nitrogen recovery as single cell protein from biogas slurry. The maximum biomass of 6.2 g/L with protein content of 53.5% was produced in batch cultivation with glucose as the carbon source, C/N ratio of 3:1, NH4+-N concentration of 3000 mg/L, initial pH of 8.0, and the addition of 0.35% (w/v) Na2HPO4. It was speculated that C. utilis can grow well with free ammonia below 197 mg/L. In fed-batch fermentation, a biomass of 14.8 g/L was obtained, and the maintenance of aerobic conditions was critical to improving the production of single cell protein. The sterilized and non-sterilized biogas slurry can be used as an effective pH regulator. The obtained single cell protein was a nutritious, safe, and reliable protein source. This study provides novel insights into nitrogen recovery via C. utilis as a single cell protein from biogas slurry.

Single-Cell Protein Production as a Strategy to Reincorporate Food Waste and Agro By-Products Back into the Processing Chain.

Food waste is a serious problem with negative environmental and economic consequences. Unused food (either as waste or by-products and referred to as food residues in the present work) is a source of carbohydrates, lipids, proteins, vitamins, minerals and bioactive compounds that could be used in an alternate or secondary life cycle to avoid discarding it. The present work reviews the potential use of food residues for the bioengineering of single-cell protein (SCP), addressing aspects of production, nutrition and safety, as well as the main challenges and perspectives. SCP is obtained from various microorganisms, including fungi, bacteria, yeasts and algae, in pure or mixed form. SCP generally contains a higher percentage of protein (30-80%) compared to soy (38.6%), fish (17.8%), meat (21.2%) and whole milk (3.28%). SCP is a source of essential amino acids, including methionine, threonine and lysine. The use of food residues as substrates for the production of SCP would reduce production costs (35-75%); however, optimization and industrial scaling are some of the main challenges to its sustainable production. The use food waste and agro by-products from the food industry could be a promising alternative to obtain protein according to a circular production scheme.