Enhancing biocontrol efficacy of Cryptococcus laurentii induced by carboxymethyl cellulose: Metabolic pathways and enzyme activities insights

The synergistic biocontrol effects of Cryptococcus laurentii cultured with carboxymethyl cellulose (CMC) were studied to control Penicillium italicum in postharvest grapefruit. The results showed that C. laurentii was cultured in 0.5 % (w/v) CMC (CMC-C. laurentii) significantly inhibited elongation of germ tubes, decreased germination of conidia in P. italicum, and reduced disease in grapefruit. Besides, CMC significantly increased ATP synthase and population proliferation of C. laurentii. Moreover, metabolomics analysis revealed 24 significantly differentially metabolites in CMC-C. laurentii including the citrate cycle, metabolism of glyoxylic acid, dicarboxylic acid, phenylalanine, tyrosine, and tryptophan and amino acid biosynthesis. These results demonstrate that CMC could significantly enhance the ATP synthase by promoting the citrate cycle, providing energy for strain growth, and thereby increasing the biocontrol effectiveness of C. laurentii. Furthermore, adding CMC enhanced the activities of strain extracellular hydrolases and antioxidases, which increased the resistance to stress, thus improving the antagonistic effect of C. laurentii.