从新疆传统发酵乳中筛选出具有蛋白水解活性的酵母菌，对其发酵乳进行蛋白水解和体外自由基清除活力测定；并与商业酸奶发酵剂（L. bulgaricus subsp. CICC6047和 S. thermophilus CICC6038）复配，研究其在发酵以及冷藏过程中发酵剂活力、蛋白水解、质构变化、酸化能力和体外自由基清除活力的影响。结果发现，菌株0807-39具有较高的蛋白水解活性，亮氨酸含量达到0.34 mg/mL，显著高于其他菌株（p<0.05）；其发酵乳具有较高的ABTS和DPPH自由基清除率，分别为68.13%和74.24%；菌株0807-39不产生有害生物胺，对抗生素耐药敏感，且不具备溶血性，是安全性菌株；经过26SrDNA测序，鉴定为马克思克鲁维酵母菌（K. marxianus DPUL-F15）。K. marxianus DPUL-F15增加了发酵过程中乳酸菌活菌数量、乳蛋白的水解；在冷藏过程中，K. marxianus DPUL-F15显著促进发酵乳中α-酪蛋白和β-酪蛋白的降解（p<0. 05），分别降低了0.24 mg/mL和1.23 mg/mL；发酵乳中游离氨基酸的含量增加了0.1 mg/mL；加速了发酵乳后酸化，冷藏21 d时酸度达到120.56 T°；冷藏14 d时，有最高ABTS和DPPH自由基清除活性，分别为68.87%和71.1%；同时对质构特性有一定影响。因此， K. marxianus DPUL-F15具有作为一株附属发酵剂的潜力，提高发酵乳的蛋白水解。

Yeast strain with proteolytic activity was screened from traditional fermented milk in Xinjiang, and its proteolytic activity and free radical scavenging activity in vitro were determined. It was compounded with commercial yogurt starter (Lactobacillus bulgaricus subsp. CICC6047 and Streptococcus thermophilus CICC6038) to study the effects of starter activity, protein hydrolysis, texture change, acidification ability and free radical scavenging activity in vitro during fermentation and storage. The results showed that strain 0807-39 had high proteolytic activity, and the Leucine content reached 0.34 mg/mL, which was significantly higher than other strains (P < 0.05). The free radical scavenging rates of ABTS and DPPH in fermented milk were 68.13% and 74.24% respectively. Strain 0807-39 does not produce harmful biogenic amines, is sensitive to antibiotic resistance, and does not have hemolysis, so it is a safe strain. 26 SrDNA sequencing showed that it was identified as K. marxianus DPUL-F15. K. marxianus DPUL-F15 promoted the number of viable lactic acid bacteria and increased the hydrolysis of milk protein in the fermentation process, and the leucine content at the end of fermentation was 0.52 mg/ml. During cold storage, K. marxianus DPUL-F15 significantly promoted the degradation of α-casein and β-casein in fermented milk (p<0. 05), which decreased by 0.24 mg/mL and 1.23 mg/ml respectively. Meanwhile, the content of free amino acids in fermented milk increased by 0.1 mg/ml. The post-acidification of fermented milk was accelerated, and the acidity reached 120.56 T°；after 21 days of storage. After 14 days of storage, the scavenging activities of ABTS and DPPH free radicals were the highest, which were 68.87% and 71.1% respectively. At the same time, it has certain influence on texture characteristics. Therefore, K. marxianus DPUL-F15 has the potential to serve as an adjunct starter to improve proteolysis of fermented milk.

新疆传统发酵制品中菌种资源收集，微生物多样性分析及特色特色乳制品开发应用