Open-mixed fermentative culture as a feasible strategy to valorize agroindustrial residues into lactic acid

Lactic acid (HLact) is a platform chemical with wide industrial applications, and its production from waste streams offers a cost-effective alternative to conventional feedstock. However, pure bacterial cultures represent one of the highest costs of the production process due to the axenic conditions required. In this work, anaerobic fermentation of agroindustrial waste (AGW) was conducted at pH 4.5 and 25 °C using the indigenous microbiota naturally present in the AGW as sole microbial source. The process achieved a stable HLact accumulation of 33.2 g · L^-1 in the absence of pretreatment, corresponding to 48.3% bioconversion of organic matter. Microbial community analysis in terms of abundance revealed the predominance of the Lactobacillaceae family (56.4%) and Lactobacillus genus (36.3%), which contributed to the high selectivity towards HLact (87.7% w/w). These results highlighted the potential of open-mixed fermentative cultures for HLact production without the need for costly pretreatments or axenic conditions, thereby increasing the cost-effectiveness of the process.