Screening, Identification and Genome Annotation of Esterase-Producing Lactococcus garvieae

Abstract

In this study, a strain, named S5-4, with high esterase activity was obtained from Nongxiangxing Daqu by primary and secondary screening, and subjected to whole genome sequencing, esterase annotation and metabolic pathway analysis. The strain exhibited a maximal ratio of transparent zone diameter to colony diameter (D/d) of 2.27 ± 0.02, and it was identified as Lactococcus garvieae. Its morphological, physiological, and biochemical characteristics were determined, and its esterase activity was measured to be 15.74 U/mL. This strain produced (0.345 0 ± 0.160 0) g/L of ethyl acetate and (0.298 3 ± 0.230 0) g/L of ethyl lactate after anaerobic fermentation at 35 ℃ for 15 days. The genome size of S5-4 was determined to be 2 191 113 bp in length, with a GC content of 37.99%. A total of 1 486 genes, including 4 rRNA genes, 69 tRNA genes, and 34 ncRNA genes were predicted. In total, 11 esterase genes were annotated in the genome of S5-4 including phosphatases (five intracellular ones and two membrane ones), acyl-CoA dehydrogenase (intracellular), triacylglycerol lipase (extracellular), carboxylase (extracellular), and hemicellulose esterase (intracellular). Based on functional genomic annotation, the metabolic pathways to produce ethyl acetate and ethyl lactate from starch and galactose as carbon sources were constructed and found to be consistent with the experimental results. Given its ability to produce esterase, the strain could be used as a biocatalyst for esterification in baijiu fermentation or as a flavor enhancer in Daqu production.

Keywords

• lactococcus garvieae; genomic information; metabolic pathway reconstruction; esterase