Abstract:
Optimal production conditions for alpha-L-arabinofuranosidase, one of the xylan debranching enzymes, by Streptomyces sp. PC22 were investigated. Among various sources of commercial available xylan which were from oat spelts, birchwood, and beachwood, oat spelt xylan was the best carbon source. Oat-spelt xylan at the optimal concentration of 1.0% (w/v) with a suitable organic or inorganic nitrogen source which was polypeptone or NH[subscript 4]NO[subscript 3] at the concentration equivalent to 0.05% nitrogen (w/v), the maximum enzyme activities of 0.21 and 0.36 U.ml[superscript-1] were obtained, respectively, when cultivated for 2 days at the initial pH of 8. When xylan-containing agricultural materials including wheat bran, rice bran, rice straw, corn hulls, corn cobs, cotton seed hulls and saw dust were used as a carbon source in place of the commercial xylan, among them wheat bran was found to be the best. Wheat bran at the optimal concentration of 3.0% (w/v) along with suitable organic nitrogen, polypeptone, at the concentration equivalent to 0.05% nitrogen (w/v) or inorganic nitrogen, (NH[subscript 4])[subscript 2]SO[subscript 4], at the concentration equivalent to 0.1% nitrogen (w/v), the activities obtained were higher than those by the commercial xylan with maximum values of 0.48 and 0.84 U.ml[superscript-1], respectively, after 2 days of cultivation at initial pH of 10. Preliminary study on the enzyme properties revealed that it had temperature and pH optima of 65 degree ceisius and 6.0, respectively. In addition it was found that the enzyme was stable to temperature up to 60 degree celsius for 30 min but completely lost its activity upon preincubation for 30 min at 75 degree celsius while it was stable to a wide range of pH from 5.0 - 9.0.