Sustainable production of a bioinoculant and lactic acid from a native lactic acid strain Pediococcus acidilactici A40: The role of nitrogen sources.

Abstract

The development of cost-effective and sustainable microbial inoculants is essential to promote environmentally friendly agricultural practices and circular bioeconomy strategies. In this study, a native strain of Pediococcus acidilactici A40 was cultivated using low-cost organic nitrogen sources to produce viable biomass intended for application as a silage bioinoculant, while simultaneously generating lactic acid (LA) as a value-added co-product that can be further processed as an ingredient for food technology purposes. An experimental mixture design (EMD) was applied to evaluate yeast extract (YE), corn steep liquor (CSL), and hydrolysed soybean protein (HSP) as nitrogen sources. The influence of these sources on cell viability and LA concentration was assessed, and a cost–benefit analysis (CBA) was conducted to determine the most economically viable fermentation medium. Results showed that the partial substitution of YE (40 %) with CSL (60 %) maintained high cell viability (>11 log CFU/g dry biomass (DB)) and acceptable LA concentrations. This combination achieved a 22.85% reduction in medium cost and outperformed the YE-only medium in terms of overall economic efficiency. Desirability analysis indicated that the CSL–YE combination provided an optimal balance between performance and cost. This study contributes to the valorisation of native microbial resources and agro-industrial byproducts, aligning with the principles of bioeconomy. By addressing the need to explore alternative nitrogen sources in biotechnological processes —a key strategy to enhance process sustainability—, the proposed dual-purpose bioprocess supports the development of affordable, locally produced bioinputs and bioproducts for agricultural and industrial sectors, offering a practical alternative to reduce reliance on imported inputs and to strengthen circularity in production chains.