A study revealing mechanisms behind the stone cell of Yali pear degradation by mixed-culture fermentation of lactic acid bacteria and yeast

The presence of stone cells in pears is recognized as a problem for the pear processing industry. Bacillus and mold can degrade stone cells because of their potential to digest cellulose and lignin, but they cannot be used for the degradation test of pear stone cells. In this study Lactoplantibacillus plantarum JYLP-326 was used in single culture or in the mixed culture with Saccharomyces cerevisiae Y2 to study their potential to degrade stone cells during fermentation and the mechanism of degradation was further explored. Synergy in cellulase activity was observed in the mixed-culture where the maximum activity was observed at 96th hour of fermentation. Activities of endoglucanase, exoglucanase and β-glucosidase were 1.75, 4.58, and 2.31. The degradation rate of stone cells in the mixed-culture was 37.67%, which was significantly higher than that the results obtained for single cultures. The results of scanning electron microscopy (SEM) showed that the surface of the cultured stone cells became rough. Metabolomics studies confirmed the presence of specific metabolites related to the degradation of stone cells after the fermentation. It was concluded that the mixed-culture fermentation using the above-mentioned strains could be exploited by the pear processing industry to degrade stone cells.