生淀粉糖化菌的选育及发酵条件

Studies on Screening of Raw-starchglucoamylase Producing Strain and Fermentation Conditions

以黑曲霉(Aspergillus niger)523原生质体为对象,经激光、紫外线和亚硝基胍复合诱变,选育出高产生淀粉糖化酶突变株黑曲霉NL-3,其生淀粉酶活力为156μ/ml.产酶最适培养条件为:起始pH4.5,30℃,72小时.K^+、Mg^(2+)对NL—3产生淀粉糖化酶有促进作用;Z_n^(2+)对产酶有抑制作用.酶的最适作用条件为:以玉米淀粉为底物时最适温度50℃,最适pH4.5;以甘薯淀粉、马铃薯淀粉为底物时最适温度60℃,最适pH4.0—4.5.酶在60℃保温15分钟,玉米淀粉为底物的酶剩余活力80%.甘薯淀粉、马铃薯淀粉为废物的酶剩余活力98%.

A mutant strain NL-3 with high yield of Raw-starch digesting Gluooamylase was obtained from Protoplast of Asperillus niger 523(MNNG) and treat with Laser &UV radiation. The enzyme activities were 156 u/ml. The optimal culture conditions were found: initial Ph4. 5 at 30℃ for 72h. K^(+)Mg^(2+) enhanced the enxyme activity, whereas Zn2+inhibited it .The optimal conditions for enzyme catalysis were Ph4. 5at50℃ for corn starch and Ph4.0 - 4.5 for sweat potato starch and potato starch. After incubation at 60℃ for 15min, enzyme kept 80% activity for corn starch , and 98% activity for sweat potato starch and potato starch.