影响深红酵母和白地霉产生胞外蛋白和多肽的因素

采用白地霉2.498-47在以蛋白胨为氮源发酵时,只在开始pH3.2左右产生胞外蛋白,NH_4~+则无此限制,还有助于胞外多肽的产生。深红酵母2.280胞外蛋白的最大产率约在pH5.8;尿素作唯一氮源效果最好,与蛋白胨合并使用,可产胞外蛋白约800μg/ml。酵母膏对生长和产胞外蛋白很必要,不能用玉米浆和麦芽汁代替。用0.05N NaOH浸洗不同pH和氮源所培养的细胞都能浸出胞内蛋白,接近400μg/ml。发酵产生胞外蛋白自一日后开始,至二日接近最大量,以后逐渐减少。多肽产生起自第二日,五日未达到最大量。两株酵母菌都不表现蛋白酶活性,因此这个现象还不能解释。

COMPARATIVE STUDY OF PH AND NITROGEN SOURCES ON THE EXTRACELLULAR PROTEIN AND POLYPEPTIDE PRODUCTION BY RHODOTORULA RUBRA AND GEOTRICUM CANDIDUM STRAINS

The conditions of extracellular protein (EP) and polypeptide (EPP) production from peptone and inorganic nitrogen sources containing medium by strains of Rhodotorula rubra 2.280 and Geotricum candidum 2.498—47 are determined. EP and EPP production of 2.498—47 in peptone medium only occurred in the range of pH 3.05—3.93 and no pH limitation with salts of NH~_4~+. Moreover, NH_4~+ was found to be favourable to EPP production. For 2.280, no pH limitation occurred in peptone or NH_4~+, and maximum productivity occurred at pH 8, and more than 800 μg/ml EP was produced when urea was used as nitrogen source. Yeast extract was essential for both strains in growth and EP and EPP production, and it could not be substituted by cornsteep-liquor or malt extract. All cells of both strains grown in different pH and nitrogen sources could release endocellular protein about 400μg/ml when steeped with diluted alkali solution. EP production in fermentation began after first day, reached maximum in the second day, and decreased afterwards. As no proteinase activity was detected, the reason of this protein decrease remained unknown.