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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黑曲霉生产果胶酶和 α-半乳糖苷酶用于酶促大豆加工

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对蛋白质的需求。为了富集大豆蛋白，环境友好的酶促加工需要多种糖酶，包括纤维素酶、木聚糖酶、果胶酶、α-半乳糖苷酶和蔗糖酶。除了富含蛋白质外，该加工过程还通过生成单糖来增加价值，这些单糖是生物燃料/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技术差距。糖酶生产菌株 A. niger (NRRL 322) 与大豆壳一起用作诱导底物。温度为 20 °C，发现 25 °C 和 30 °C 会影响细胞在蔗糖上的生长，阿伦尼乌斯定律激活能为 28.7 kcal/mol。30°C 促进了最快的细胞生长（倍增时间 = 2.1 小时）和最早的酶产生，但由于较早的碳源耗竭，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。与具有恒定 pH 值 4 的发酵相比，初始 pH 值为 6 或 7 的发酵产量最高，例如，72 小时后产生 1.9 至 2.3 倍的果胶酶和 2.2 至 2.3 倍的 α-半乳糖苷酶。 ，pH 值必须保持在 2.6 以上以避免果胶酶生产受到限制，并且在后期的底物限制阶段，pH 值必须保持在 5.5 以下以避免果胶酶降解。α-半乳糖苷酶的产生总是滞后于果胶酶的产生，滞后 16-24 小时；据推测，前者依靠果胶水解产生诱导剂。最佳酶生产需要控制诱导剂的瞬时可用性。