CELLULASES OF PLANT AND MICROBIAL ORIGIN IN GERMINATING BARLEY

Abstract

Cellulase activity in crude extracts of germinating barley is at least five-fold higher in hulled than in hull-less cultivars. Surface sterilization of the grain prior to germination reduces cellulase to levels that are similar in all cultivars. In hulled barley most of the cellulase detected during germination is probably of microbial origin, but there is circumstantial evidence to suggest that significant activity can also be attributed to cellulases of plant origin. The micro-organisms associated with germinating grain reside largely in the hull and the major fungal species present on the hulled variety Clipper were Aureobasidium pullulans, Rhizopus stolonifer and Penicillium spp. Surface sterilization of the grain with silver nitrate, followed by steeping in a solution containing antibiotics, completely eliminated microbial growth on hull-less cultivars. After similar treatment of a hulled barley two yeasts could be detected. The results emphasize the importance of eliminating microbial growth prior to studies of polysaccharide hydrolases which develop during the germination of barley and which are assumed to be of plant origin.