Evaluation of Solid-State Fermentation Potential of Sweet Sorghum Stalk by Heyndrickxia coagulans (Bacillus coagulans) L-2 Based on Complete Genome and Phenotypic Analysis.

Heyndrickxia coagulans is the dominant strain in L-lactic acid fermentation. To promote the development of green and low-cost L-lactic acid fermentation processes, it is crucial to understand their solid-state fermentation (SSF) performance in lignocellulose raw materials. This study presents the first whole genome analysis of H. coagulans L-2 (single chromosome, 3.58 Mb, 46.28% GC content) to evaluate its SSF potential using sweet sorghum stalk. COG and KEGG annotations revealed that H. coagulans L-2 metabolizes diverse hexoses and pentoses for L-lactic acid production, and the key enzymatic sequences in carbohydrate metabolism exhibited high similarity with other Heyndrickxia strains. Comparative genomics with ATCC7050 demonstrated 70% genome similarity (2148 collinear CDSs), while L-2 has a more comprehensive carbohydrate metabolism network, especially in pentose metabolism pathways, such as arabinose, mannose, and rhamnose. Through the result of batch solid fermentation, H. coagulans L-2 could promote the re-fermentation of L-lactic acid in silage and reduce heterotypic lactic acid fermentation (lactic acid/ethanol ratio increased from 3.890 to 8.103), which indicated that the strain L-2 played a key role in the SSF of sweet sorghum silage and promoted the production of bio-based materials precursors of sweet sorghum. This study provides a new strategy for the high-value utilization of lignocellulosic biomass.