Lignocellulose Degrading Weizmannia coagulans Capable of Enantiomeric L-Lactic Acid Production via Consolidated Bioprocessing

Abstract

Second-generation lactic acid production requires the development of sustainable and economically feasible processes and renewable lignocellulose biomass as a starting raw material. Weizmannia coagulans MA42 was isolated from a soil sample in Chiang Mai province, Thailand and showed the highest production of L-lactic acid and lignocellulolytic enzymes (cellulase, β-mannanase, xylanase, β-glucosidase, β-mannosidase, and β-xylosidase) compared to other isolates. Weizmannia coagulans MA42 was able to grow, secrete lignocellulolytic enzymes, and directly produce L-lactic acid in the medium containing various lignocellulosic feedstocks as the sole carbon source. Moreover, L-lactic acid production efficiency was improved after the substrates were pretreated with diluted sulfuric acid and diluted sodium hydroxide. The highest L-lactic acid production efficiency of 553.4 ± 2.9, 325.4 ± 4.1, 326.6 ± 4.4, 528.0 ± 7.2, and 547.0 ± 2.2 mg/g total available carbohydrate was obtained from respective pretreated substrates including sugarcane bagasse, sugarcane trash, corn stover, rice straw, and water hyacinth. It is suggested that structural complexity of the lignocellulosic materials and properties of lignocellulolytic enzymes are the key factors of consolidated bioprocessing (CBP) of lignocellulosic feedstocks to lactic acid. In addition, the results of this study indicated that W. coagulans MA42 is a potent bacterial candidate for CBP of a variety of lignocellulosic feedstocks to L-lactic acid production; however, further bioprocess development and genetic engineering technique would provide higher lactic acid production efficiency, and this would lead to sustainable lactic acid production from lignocellulosic feedstocks.