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

Abstract

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.