Valorization of Xylose-Rich Medium from Cynara cardunculus Stalks for Lactic Acid Production via Microbial Fermentation

Lactic acid (LA) is a versatile, optically active compound with applications across the food, cosmetics, pharmaceutical, and chemical industries, largely driven by its role in producing biodegradable polylactic acid (PLA). Due to its abundance, lignocellulosic biomass is a promising and sustainable resource for LA production, although media derived from these matrices are often rich in xylose and contain growth inhibitors. This study investigates LA production using a xylose-rich medium derived from <i>Cynara cardunculus L. altilis</i> DC stalks treated through steam explosion and enzymatic hydrolysis. The lactic acid bacteria strains <i>Lacticaseibacillus casei</i>, <i>Paucilactobacillus vaccinostercus</i>, and <i>Pediococcus pentosaceus</i> were grown on natural media, achieving yields of 0.59, 0.57, and 0.58 g LA/g total carbon consumed, respectively. Remarkably, on xylose-rich media, all supplied sugar was consumed, with LA yields comparable to those on complex media. These findings highlight the adaptability of these strains in the presence of inhibitors and support the potential of lignocellulosic biomass as a low-cost and sustainable substrate for effective PLA production.