Soybean is a most promising sustainable protein source for feed and food to help meet the protein demand of the rapidly rising global population. To enrich soy protein, the environment-friendly enzymatic processing requires multiple carbohydrases including cellulase, xylanase, pectinase, α-galactosidase and sucrase. Besides enriched protein, the processing adds value by generating monosaccharides that are ready feedstock for biofuel/bioproducts. Aspergillus could produce the required carbohydrases, but with deficient pectinase and α-galactosidase. Here we address this critical technological gap by focused evaluation of the suboptimal productivity of pectinase and α-galactosidase. A carbohydrases-productive strain A. niger (NRRL 322) was used with soybean hull as inducing substrate. Temperatures at 20 °C, 25 °C and 30 °C were found to affect cell growth on sucrose with an Arrhenius-law activation energy of 28.7 kcal/mol. The 30 °C promoted the fastest cell growth (doubling time = 2.1 h) and earliest enzyme production, but it gave lower final enzyme yield due to earlier carbon-source exhaustion. The 25 °C gave the highest enzyme yield. pH conditions also strongly affected enzyme production. Fermentations made with initial pH of 6 or 7 were most productive, e.g., giving 1.9- to 2.3-fold higher pectinase and 2.2- to 2.3-fold higher α-galactosidase after 72 h, compared to the fermentation with a constant pH 4. Further, pH must be kept above 2.6 to avoid limitation in pectinase production and, in the later substrate-limiting stage, kept below 5.5 to avoid pectinase degradation. α-Galactosidase production always followed the pectinase production with a 16-24 h lag; presumably, the former relied on pectin hydrolysis for inducers generation. Optimal enzyme production requires controlling the transient availability of inducers.

中文翻译：

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黑曲霉生产用于酶法大豆加工的果胶酶和 α-半乳糖苷酶


大豆是饲料和食品中最有前途的可持续蛋白质来源，有助于满足快速增长的全球人口的蛋白质需求。为了丰富大豆蛋白，环保的酶处理需要多种糖酶，包括纤维素酶、木聚糖酶、果胶酶、α-半乳糖苷酶和蔗糖酶。除了丰富的蛋白质之外，加工还通过产生单糖来增加价值，单糖是生物燃料/生物产品的现成原料。曲霉可以产生所需的糖酶，但缺乏果胶酶和α-半乳糖苷酶。在这里，我们通过重点评估果胶酶和 α-半乳糖苷酶的次优生产力来解决这一关键的技术差距。使用产糖酶菌株 A. niger (NRRL 322) 和大豆皮作为诱导底物。研究发现 20 °C、25 °C 和 30 °C 的温度会影响蔗糖上的细胞生长，阿伦尼乌斯定律活化能为 28.7 kcal/mol。 30°C 促进最快的细胞生长（倍增时间 = 2.1 小时）和最早的酶产生，但由于较早的碳源耗尽，最终酶产量较低。 25°C 的酶产量最高。 pH 条件也强烈影响酶的产生。与恒定pH 4的发酵相比，初始pH 6或7进行的发酵是最高产的，例如，72小时后产生高1.9至2.3倍的果胶酶和高2.2至2.3倍的α-半乳糖苷酶。 ，pH 必须保持在 2.6 以上，以避免果胶酶生产受到限制，并且在后期底物限制阶段，pH 必须保持在 5.5 以下，以避免果胶酶降解。 α-半乳糖苷酶的产生总是跟随果胶酶的产生，有 16-24 小时的滞后；据推测，前者依赖果胶水解来产生诱导剂。 最佳的酶生产需要控制诱导剂的瞬时可用性。