Abstract

L-asparaginases prevent the formation of acrylamide, a substance commonly found in foods subjected to heat and that also contains reducing sugars and L-asparagine. This work aimed to select a strain of Aspergillus spp. able to produce L-asparaginase and to optimize the fermentation parameters, the partial purification and biochemical characterization were also performed. The Aspergillus oryzae IOC 3999 was selected due to its greater enzymatic activity: 1443.57 U/mL of L-asparaginase after 48 h of fermentation. The optimized conditions allowed for an increase of 223% on the L-asparaginase production: 2.9% lactose, 2.9% L-asparagine and 0.7% hydrolyzed casein, 0.152% KH₂PO₄, 0.052% KCl and MgSO₄, 0.001% of CuNO₃.3H₂O, ZnSO₄.7H₂O and FeSO₄.7H₂O adjusted to pH 7.0; added a concentration of 5.05x10⁶ spores/mL at 30 °C for 100 rpm. A purification factor of 2.11 was found and the molecular mass was estimated at 20.8 kDa. The enzyme showed optimum activity at 60 °C and pH 5 and stability at 50 °C for 1 h. The enzyme presented desirable biochemical characteristics, mainly the acid pH stability, indicating that the enzyme would work well in food matrices due to the closeness of pH, meaning that it could be a potential option for use in the food industry.

摘要

L-天冬酰胺酶可防止丙烯酰胺的形成，丙烯酰胺是一种常见于受热食物中的物质，还含有还原糖和 L-天冬酰胺。这项工作旨在选择一株曲霉属。能够生产L-天冬酰胺酶并优化发酵参数，还进行了部分纯化和生化表征。选择米曲霉IOC 3999 是因为它具有更高的酶活性：发酵 48 小时后 L-天冬酰胺酶的含量为 1443.57 U/mL。优化条件允许 L-天冬酰胺酶产量增加 223%：2.9% 乳糖、2.9% L-天冬酰胺和 0.7% 水解酪蛋白、0.152% KH ₂ PO ₄、0.052% KCl 和 MgSO ₄, 0.001% 的 CuNO ₃ .3H ₂ O、ZnSO ₄ .7H ₂ O 和 FeSO ₄ .7H ₂ O 调节至 pH 7.0；添加浓度为 5.05x10 ⁶孢子/mL 在 30 °C 下 100 rpm。发现纯化因子为 2.11，分子量估计为 20.8 kDa。该酶在 60 °C 和 pH 值 5 下显示出最佳活性，并在 50 °C 下保持 1 小时稳定。该酶具有理想的生化特性，主要是酸性 pH 稳定性，表明由于 pH 值接近，该酶在食品基质中表现良好，这意味着它可能成为食品工业的潜在选择。