Microbial conversion of agro-wastes for lactic acid production

Abstract

Lactic acid (LA) is an organic compound produced via fermentation by microorganisms that can utilize a wide range of carbohydrate sources and has gained relevance in food industries for preservation, pharmaceutical industries as additives, textile industries as mordants and production of cosmetics and bioplastics. In spite of the various applications of lactic acid, its availability is a challenge, especially in developing countries like Nigeria and therefore has to be imported, making it very expensive. One of the core substrates for lactic acid production is glucose. This study focused on the production of lactic acid using reducing sugar from locally sourced agro-wastes (corncob, sugarcane bagasse, plantain peduncle and groundnut shell). Bacteria were isolated from the agro-wastes dumpsite and screened for lactic acid production using De Man Rogosa and Sharpe (MRS) agar. The agro-wastes were pretreated using NaOH and hydrolyzed using cellulase produced from Aspergillus niger. The lactic acid bacteria (LAB) were identified based on their cultural, morphological, biochemical and molecular characteristics. The screened isolates were used for the production of lactic acid in an MRS medium containing the agro-waste hydrolysates as the sole carbon source. The LAB isolate with the best ability for lactic acid production was ascertained using the spectrophotometric method. Eleven (11) isolates were obtained from the agro-wastes dumpsites. Lactiplantibacillus plantarum (accession number OM510300) from plantain peduncle dumpsites had the highest potential for lactic acid production (1.9558 g/L). The study revealed that Nigerian-locally sourced agro-wastes can be developed as an alternative source of reducing sugar for lactic acid production and thus leads to agro-wastes management in the environment.