Effects of fermentation by Ganoderma lucidum and Saccharomyces cerevisiae on rape pollen morphology and its wall

This study investigated the mechanism of wall rupture fermentation of the rape bee pollen by Ganoderma lucidum and Saccharomyces cerevisiae. The enzymatic activities and broken-wall ratios were determined, and the results suggested the involvement of cellulase, protease, and pectinase in the wall rupture fermentation. Among the five substrate inducers, CMCase, protease, and pectinase had the highest enzymatic activities at 23.13 ± 1.09, 63.44 ± 1.35, and 118.61 ± 2.07 U/mL, respectively. The broken-wall ratios of G. lucidum and S. cerevisiae were 85.08 ± 3.92 and 88.31 ± 2.51%, respectively. The wall rupture of rape pollen was closely related to the enzymes of the fermenting species. The wall rupture process was determined through enzyme assay, light microscopy, and scanning electron microscopy, and the broken-wall ratios provide further information on the said mechanism. The process follows three steps, namely, removal of coating on the pollen surface, continuous opening of three germinal apertures to allow enzymatic breakdown of the intine, and release of contents from the degradation of the exine.