Lactic Acid Production from Sugarcane Bagasse Hydrolysates by Lactiplantibacillus Strains

Lactic acid (LA) is a valuable organic acid widely used in many industries and bioplastics production. It can be produced by microbial fermentation of sugarcane bagasse (SCB), an abundant sugar industry waste rich in cellulose and hemicellulose. The aim of this study was to evaluate the ability of lactic acid bacteria to ferment pentoses from SCB hydrolysates for LA production in the presence or absence of hexoses. Initially, nine strains of Lactiplantibacillus spp. were screened for efficient xylose consumption. Subsequently, fermentation assays with the selected strain were performed in 2 L bioreactors using MRS-based media containing either hemicellulosic or total hydrolysates obtained from steam-exploded SCB. Among the nine strains, Lactiplantibacillus pentosus (L. pentosus) ATCC 8041 demonstrated superior xylose assimilation and LA production. Additionally, this strain was capable of consuming xylose in the presence of glucose, achieving an LA yield of 0.78 g/g and a maximum LA concentration of 28.99 g/L for MRS_TH media. The MRS_HEM was highly diluted, resulting in a maximum LA concentration and yield of 2.4 and 0.65 g/g, respectively. These results highlight the potential of L. pentosus ATCC 8041 to utilize both hemicellulose and cellulose fractions of SCB, offering promising avenues for sustainable lactic acid production from agroindustrial residues.