Optimization of fermentation parameters for enhanced and low-cost production of single-cell protein from rice polishing using <i>Rhizopus oligosporus</i>

A growing concern over food shortages caused by the expanding world population has led to the use of unconventional substitutes for food sources, such as single-cell protein (SCP) produced from microbes using inexpensive feedstock and wastes. The fungal strain Rhizopus oligosporus can consume different substrates, and thus has been used for the production of several products for human and animal consumption. There are very few reports on using rice polishing for SCP production from microbes; however, there is no information regarding the use of R. oligosporus. This study aimed to optimize the process parameters to investigate the possibility of enhanced bioconversion of rice polishing into SCP using R. oligosporus in comparison with the control medium (glucose). Proximate composition of rice polishing as a potential substrate was estimated, and the effects of process variables on biomass and protein content were elucidated. The optimum conditions including substrate concentration 8%, temperature 30°C, pH 5.5, inoculum size 5%, fermentation period 96 h, and optimum amount of supplements in the medium were found to give a considerable biomass (19.5 ± 1.93 g/L) and protein content (49.5 ± 0.9%), which are comparable with the control medium. The optimum conditions were verified and statistically analyzed through confirmatory experiments in triplicate.