Production of Single Cell Protein and Polyhydroxyalkanoate from Carica papaya Waste

A comprehensive report on valorization of waste to single cell protein: strategies, challenges, and future prospects

The food insecurity due to a vertical increase in the global population urgently demands substantial advancements in the agricultural sector and to identify sustainable affordable sources of nutrition, particularly proteins. Single-cell protein (SCP) has been revealed as the dried biomass of microorganisms such as algae, yeast, and bacteria cultivated in a controlled environment. Production of SCP is a promising alternative to conventional protein sources like soy and meat, due to quicker production, minimal land requirement, and flexibility to various climatic conditions. In addition to protein production, it also contributes to waste management by converting it into food and feed for both human and animal consumption. This article provides an overview of SCP production, including its benefits, safety, acceptability, and cost, as well as limitations that constrains its maximum use. Furthermore, this review criticizes the downstream processing of SCP, encompassing cell wall disruption, removal of nucleic acid, harvesting of biomass, drying, packaging, storage, and transportation. The potential applications of SCP, such as in food and feed as well as in the production of bioplastics, emulsifiers, and as flavoring agents for baked food, soup, and salad, are also discussed.

PHB production by Bacillus megaterium strain MNSH1-9K-1 using low-cost media

Plastics are widely used for diverse applications due to their versatility. However, their negative impact on ecosystems is undeniable due to their long-term degradation. Thus, there is a rising need for developing eco-friendlier alternatives to substitute fossil-based plastics, like biopolymers. PHA are synthesized intracellularly by microorganisms under stressful conditions of growth and have similar characteristics to conventional polymers, like their melting point, transition temperatures, crystallinity, and flexibility. Although it is feasible to use biopolymers for diverse industrial applications, their elevated production cost due to the supplies needed for microbiological procedures and the low productivity yields obtained have been the main limiting factors for their commercial success. The present study assessed the ability of Bacillus megaterium strain MNSH1-9K-1 to produce biopolymers using low-cost media from different kinds of fruit-peel residues. The results show that MNSH1-9K-1 can produce up to 58 g/L of PHB when grown in a medium prepared from orange-peel residues. The data obtained provide information to enhance the scalability of these kinds of biotechnological processes.

Valorization of pineapple peel waste for fungal pigment production using Talaromyces albobiverticillius: Insights into antibacterial, antioxidant and textile dyeing properties

The present study explores natural pigments as sustainable alternatives to synthetic textile dyes. Due to their therapeutic applications and easy production, fungal pigments have gained attention. However, data on pigment production using solid-state fermentation and optimization is limited. Milk whey was used to grow Talaromyces sp., followed by an evaluation of pigment production in solid and liquid media. Pineapple peels were used as a cost-effective substrate for pigment production, and a one-factor-at-a-time approach was used to enhance pigment production. Pineapple peel-based media produced 0.523 ± 0.231 mg/g of pigment after eight days of incubation. The crude pigment had promising antibacterial and significant antioxidant properties. The extraction fungal pigment's possible use as an eco-friendly textile dye was assessed through fabric dyeing experiments with different mordants. This work contributes to the valorization of agricultural waste and provides insight into using fungal pigments as sustainable alternatives to synthetic textile dyes.

Banana peels as a cost effective substrate for fungal chitosan synthesis: optimisation and characterisation

Massive accumulation of unprocessed banana peels enthralls sustainable issues as they are eventually dumped as landfills leading to emission of obnoxious gasses. To avoid these persisting challenges the present study shims lights on chitosan production from the characterised fungal strain using banana peel hydrolysate as an effective medium. Substantial amount of carbohydrate in banana peels serves as a potential solution for fungal chitosan production in a view to attain a circular bioeconomy and repurposed for synthesis of beneficial products in a cost effective manner. Presence of fermentable sugars in banana peels qualifies them as a feasible substrate which could be exploited for scaling up of fungal chitosan synthesis. Screened isolate was subjected to statistical optimisation using formulated medium to elucidate the influential factors that had significant effect on chitosan production. The harvested chitosan biomass was characterised through standardised techniques and evaluated for further studies. Statistical optimisation reveals that ammonium nitrate (5 g/L), pH (6) and incubation time (144 hrs) were the three PBD variables that had a greater influence on fungal chitosan yield. The validated developed model exhibited maximum yield of 200 mg/L, a 4.4 fold increase than unoptimised medium (45 mg/L). These findings emphasise the fermentative synthesis of chitosan through valorisation of banana peel prop up a complementary approach in concomitant with preserving renewable resources and bioproduct formation.

Single Cell Protein Production Using Different Fruit Waste: A Review

The single cell protein (SCP) technique has become a popular technology in recent days, which addresses two major issues: increasing world protein deficiency with increasing world population and the generation of substantial industrial wastes with an increased production rate. Global fruit production has increased over the decades. The non-edible parts of fruits are discarded as wastes into the environment, which may result in severe environmental issues. These fruit wastes are rich in fermentable sugars and other essential nutrients, which can be effectively utilized by microorganisms as an energy source to produce microbial protein. Taking this into consideration, this review explores the use of fruit wastes as a substrate for SCP production. Many studies reported that the wastes from various fruits such as orange, sweet orange, mango, banana, pomegranate, pineapple, grapes, watermelon, papaya, and many others are potential substrates for SCP production. These SCPs can be used as a protein supplement in human foods or animal feeds. This paper discusses various aspects in regard to the potential of fruit wastes as a substrate for SCP production.

Microbial community-based protein production from wastewater for animal feed applications

Single cell protein (SCP) derived from microbial biomass represents a promising source of protein for animal feed additives. While microbial community-based approaches to SCP production using nutrient-rich wastewaters incur lower costs than traditional single organism-based approaches, they have received little attention. This review focuses on SCP production using wastewaters with an emphasis on food-processing wastewaters. An elemental carbon-to-nitrogen ratio ranging from 10 to 20 is recommended to promote a high microbial biomass protein yield. Proteobacteria was identified as the most prevalent phylum within SCP-producing microbial communities. More research is needed to determine the composition of the microbial community best suited for SCP production, as well as its relationship with the microbial community in influent food-processing wastewaters. Remaining challenges are target protein and essential amino acids content, protein quantification and biomass yield assessment. The review presents bioreactor design considerations towards defining suitable operating conditions for SCP production through microbial community-based fermentation.

Residual biomass from surfactin production is a source of arginase and adsorbed surfactin that is useful for environmental remediation

Lipopeptides are important secondary metabolites produced by microbes. They find applications in environmental decontamination and in the chemical, pharmaceutical and food industries. However, their production is expensive. In the present work we propose three strategies to lower the production costs of surfactin. First, the coproduction of surfactin and arginase in a single growth. Second, extract the fraction of surfactin that adsorbs to the biomass and is removed from the growth medium through centrifugation. Third, use microbial biomass for the remediation of organic and inorganic contaminants. The coproduction of surfactin and arginase was evaluated by factorial design experiments using the LB medium supplemented with arginine. The best conditions for surfactin production were 22 h of growth at 37 °C using LB supplemented with arginine 7.3 g/L. Almost similar conditions were found to produce highest levels of arginase, 24 h and 6.45 g/L arginine. Decontamination of phenol and copper from artificial samples was attained by treatment with residues from lipopeptide production. Thus, cell suspensions and wash-waters used to extract surfactin from the biomass. Cell suspensions were used to successfully remove hydroquinone. Cell suspensions and wash-waters containing surfactin were successfully used to recover copper from solution. Specific monitoring methods were used for phenol and metal solutions, respectively a biosensor based on tyrosinase and either atomic absorption flame ionization spectrometry or absorbance coupled to the Arduino™ platform. Therefore, we report three alternative strategies to lower the production costs in lipopeptide production, which include the effective recovery of copper and phenol from contaminated waters using residues from surfactin production. Sustainable and profitable production of surfactin can be achieved by a coproduction strategy of lipopeptides and enzymes. Lipopeptides are collected in the supernatant and enzymes in the biomass. In addition, lipopeptides that coprecipitate with biomass can be recovered by washing. Lipopeptide wash-waters find applications in remediation and cells can also be used for environmental decontamination.

The production of single cell protein from biogas slurry with high ammonia-nitrogen content by screened Nectaromyces rattus

In this study, a novel method was proposed to obtain single cell protein (SCP) in yeast by using biogas slurry as culture medium. The results show that Nectaromyces rattus was the most efficient at producing SCP among the 7 different yeasts studied. Acetic acid was a better pH regulator than hydrochloric acid. After culture with the initial NH₄⁺-N concentration 2,000 mg/L, C/N ratio 6:1, the initial pH 5.50 and rotation speed of 200 rpm, a total cell dry weight of 12.58 g/L with 35.96% protein content was obtained. Nineteen amino acids accounted for 46.85% of cell dry weight, and proline content was as high as 12.0% of the cell dry weight. However, sulfur-containing amino acids, including methionine and cystine, were deficient. Further research should focus on the high cell density culture to increase SCP production.

Optimization of process parameters for improved production of biomass protein from Aspergillus niger using banana peel as a substrate

This study was aimed to optimize the process variables for improved production of biomass protein using Aspergillus niger from banana fruit peel by the use of response surface methodology. A five-level-four factors central composite rotatable design was applied to elucidate the influence of process variables viz. temperature (20-40 °C), pH (4-8), substrate concentration (5-25%), and fermentation period (1-5 days) on biomass and protein content. The second-order polynomial models were established, which effectively explicated the variation in experimental data and significantly epitomized the appreciable correlation between independent variables and responses. After numerical optimization, the predicted optimum conditions (temperature of 31.02 °C, pH of 6.19, substrate concentration of 19.92%, and the fermentation period of 4 days) were obtained with biomass of 24.69 g/L and protein of 61.23%, which were verified through confirmatory experiments.