Abstract: The thermotolerant Bacillus coagulans HL5-C and its mutant 5E-1 were selected as the research objects. The chemically defined media(CDM)suitable for the growth and metabolism of HL5-C and 5E-1 was screened and their fermentation characteristics were studied.The single factor addition experiment results showed that uracil in chemically defined media was the key substance affecting the growth of HL5-C in CDM,while lysine,proline and phenylalanine were the necessary components for 5E-1 growth. The CDM suitable for HL5-C and 5E-1 growth was named MCDM4,MCDM5,respectively.Then,the fermentation conditions of HL5-C and 5E-1 under single carbon source and mixed carbon source were investigated,it was found that HL5-C preferentially utilized glucose and the utilization of other non-glucose sugars was delayed,showing carbon catabolite repression(CCR). However,5E-1 produced lactic acid by metabolizing glucose and other non-available carbon sources simultaneously,which indicated that 5E-1 could effectively relieve or alleviate CCR induced by glucose. The results laid a foundation for CCR mechanism research in B. coagulans.