Production of Single Cell Protein and Polyhydroxyalkanoate from Carica papaya Waste

Abstract

Carica papaya waste represents an ideal candidate for production of single cell proteins (SCP) and polyhydroxyalkanoates (PHA) due to its high carbohydrate content. Bioconversion of papaya waste in to microbial biomass protein or SCP and PHA paves way to tackle global issues raised due to protein caloric malnutrition and synthetic plastic disposal, respectively. In this work, acid hydrolyzed papaya waste was employed as substrate for PHA and SCP production. Maximum PHA production (4.2 g/L) was observed with papaya peel under optimized conditions of temperature (37 \({^{\circ }}\)C), pH (7), carbon source (sucrose) and nitrogen source (ammonium sulfate) on 72 h of fermentation using Bacillus subtilis NCDC0671. The extracted polymer was characterized through FTIR spectroscopy. SCP production using Saccharomyces cerevisiae NDRI 364 was sequentially optimized for maximizing biomass yield. Maximum SCP production was achieved at 25 \({^{\circ }}\)C (4.67 g/L), pH 5 (4.65 g/L), incubation period of 120 h (4.86 g/L). Screening for best carbon and nitrogen source revealed that maximum SCP was produced using sucrose (4.26 g/L) and beef extract (4.56 g/L) as carbon and nitrogen source, respectively. HPTLC profile of the SCP revealed a significant amount of both essential and non-essential amino acids suggesting its possible incorporation as a feed ingredient.