Synergistic action of multiple degumming-related enzymes secreted by Bacillus subtilis XW-18: Decisive factor for driving the bio-degumming process of raw pineapple leaves

Degumming, a process of removing gummy substances surrounding fiber, plays a crucial role in preparing plant fibers. This study clearly clarified that the multiple degumming enzymes by Bacillus subtilis XW-18 acted as a decisive factor for driving bio-degumming process of raw pineapple leaves. Firstly, PCR analysis verified that B. subtilis XW-18 could produce multiple degumming-related enzymes, including 9, 24, and 1 genes encoding pectin-degrading enzymes, hemicellulose-degrading enzymes, and lignin-degrading enzyme, respectively. Subsequently, the pectin acetylesterase (PAE) from B. subtilis XW-18 was expressed in B. subtilis WB600. It was found that the engineered B. subtilis pMA5-PAE had a certain degumming effect on crushed pineapple leaves and manually extracted pineapple leaf fibers, but failed to function on raw pineapple leaves. In contrast, the wild strain B. subtilis XW-18 exerted an effective degumming effect on raw pineapple leaves. Therefore, degumming of raw pineapple leaves requires the synergistic action of multiple degumming enzymes. By using the commercial degumming enzymes for degumming of the manual extracted pineapple leaf fibers, results showed that the combination of pectinase, xylanase, and mannanase achieved a lower residual gum content than each single enzyme, further confirmed that the presence of multiple degumming enzymes contributed to a more efficient degumming progress.