Biodegradation of phthalate esters by Paracoccus kondratievae BJQ0001 isolated from Jiuqu (Baijiu fermentation starter) and identification of the ester bond hydrolysis enzyme.

Phthalate ester (PAE) pollution is an increasing problem globally. Paracoccus kondratievae BJQ0001 was isolated from the fermentation starter of Baijiu and showed an efficient degradation capability toward PAEs. To our poor knowledge, this is the first report of a P. kondratievae strain capable of degrading PAEs. The first complete genome sequence of P. kondratievae was presented without gaps, and composed of two circular chromosomes and one plasmid. The species simultaneously degraded di-methyl phthalate (DMP), di-ethyl phthalate (DEP), di-butyl phthalate (DBP), di-isobutyl phthalate (DIBP) and di-(2-ethylhexyl) phthalate (DEHP), with DMP and DEP as the preferred substrates. The half-life (t1/2) of DMP was only 6.34 h with an initial concentration of 200 mg/L. Combined with gene annotation and metabolic intermediate analysis, a metabolic pathway was proposed for the species. Benzoic acid, the intermediate of anaerobic PAE metabolism, was identified in the aerobic degradation process. Two key enzymes for alkyl ester bond hydrolysis were obtained, and belonged to families IV and VI of hydrolases, respectively. These results will promote the investigation of PAE degradation by P. kondratievae, and provide useful information for improving the quality control of food and environmental PAE treatment.

Enhanced production of ethyl acetate using co-culture of Wickerhamomyces anomalus and Saccharomyces cerevisiae.

The style and quality of Baijiu is greatly influenced by ethyl acetate. Therefore, improving and controlling the ethyl acetate levels in Baijiu is important. This study investigated ethyl acetate production using a co-culture of Saccharomyces cerevisiae Y3401 and Wickerhamomyces anomalus Y3604. More ethyl acetate was produced in mixed fermentations using both yeasts than in single fermentations. The highest ethyl acetate yield was 6.41 g/L using a Y3401/Y3604 ratio of 3:1. Synergistic fermentation using both yeasts not only improved ethyl acetate production, but also increased the contents of other flavor compounds, such as ß-phenethyl alcohol and phenethyl acetate. Therefore, the co-culture of S. cerevisiae and W. anomalus had a positive effect on ethyl acetate production and provides opportunities for altering the aroma and flavor perception of Baijiu.