Biovalorisation of mixed food waste through newly isolated thermo tolerant fungal cell factories: A step toward transforming waste to wealth

Abstract

Food waste is a lucrative biomass consisting of abundant complex organic content that can be reduced to simpler compounds and channelled towards bio-manufacturing. In this study, the hydrolysis potential of mixed food and synthetic food waste from the newly isolated fungal enzymes was examined. The screening and characterization of fungal strains with higher starch and protein degrading ability were executed. Among the isolated strains, Aspergillus terreus exhibited a better glucoamylase enzyme production rate (89 ± 4.50 U/g). The random mutagenesis of A. terreus with 150 mM EMS enhanced its glucoamylase activity by 20% as compared with the wild-type strain. The enzyme displayed its optimum activity at 55 °C, pH 5.0 with 20 min of incubation time. Metal ions such as Mn+2 and Ca+2 at 2 mM concentration upregulated the glucoamylase activity and further at 5 mM of Mn+2 concentrations the enzyme activity was augmented by about 53% enhancement as equalled with control. Strain incubation temperature had tremendous impacts on the glucoamylase activity, showing the highest activity of 193.02 ± 6.89 (U/g) and 100.03 ± 4.67 (U/g) in SFW and MFW, respectively at 37 °C under solid state fermentation. In the later stage, the food waste hydrolysis rate was improved by adapting statistical tools such as Box-Behnken design (BBD). An optimum glucose release of 0.43 (g/g) was achieved by BBD. The artificial neural network linked genetic algorithm (ANN-GA) elevated the glucose concentration further to 0.57 (g/g). The mutated strain finally produced glucose of 0.57 g/g, free amino nitrogen of 185 mg/L and 195 mg/L of inorganic phosphate. To the best of our knowledge, this is the first study, where mixed food waste is hydrolysed efficiently using A. terreus. The attained hydrolysate can be further advanced towards integrated biorefinery.