No abstract

IGUSA (Juncos effuses var. decipiens), which is commonly used to make TATAMI and Japanese flooring mats, is disposed off as a waste material in large quantities that has became a serious problem in Japan. We investigated whether this IGUSA waste could be used as a substrate by Rhizopus strains for producing glucoamylase. R. cohnii produced 1034 U/(g substrate) of glucoamylase activity from the growth medium containing the IGUSA waste. Supplementation of this growth medium with organic nitrogen sources inhibited protease production, but significantly increased (3-times or more) the glucoamylase production by R. cohnii. The most effective form of IGUSA waste was the rough powder form that retained the honeycomb structure of IGUSA. Use of the rough powder form in the growth medium increased the glucoamylase production to 9204 U/(g substrate). R. cohnii produced the similar amount of glucoamylase from all substrates (the IGUSA waste, Japanese flooring mat waste, and wheat bran) after 168 h growth. The specific activities of glucoamylase produced by R. cohnii from the IGUSA and Japanese flooring mat wastes were higher than that for the wheat bran. Thus, the method described here opens up new avenues for producing value-added products from the IGUSA waste.