The distinctive flavours in hard cheeses are attributed largely to the activity of nonstarter lactic acid bacteria (NSLAB) which dominate the cheese matrix during maturation after lactose is consumed. Understanding how different strains of NSLAB survive, compete, and scavenge available nutrients is fundamental to selecting strains as potential adjunct starters which may influence product traits. Three Lacticaseibacillus paracasei isolates which dominated at different stages over 63-week maturation periods of Australian Cheddar cheeses had the same molecular biotype. They shared many phenotypic traits, including salt tolerance, optimum growth temperature, growth on N-acetylglucosamine and N-acetylgalactosamine plus delayed growth on D-ribose, carbon sources likely present in cheese due to bacterial autolysis. However, strains 124 and 163 (later named GCRL163) survived longer at low pH and grew on D-tagatose and D-mannitol, differentiating this phenotype from strain 122. When cultured on growth-limiting lactose (0.2%, wt/vol) in the presence of high concentrations of L-leucine and other amino acids, GCRL163 produced, and subsequently consumed lactate, forming acetic and formic acids, and demonstrated temporal accumulation of intermediates in pyruvate metabolism in long-term cultures. Strain GCRL163 grew in Tween 80-tryptone broths, a trait not shared by all L. casei-group dairy isolates screened in this study. Including citrate in this medium stimulated growth of GCRL163 above citrate alone, suggesting cometabolism of citrate and Tween 80. Proteomic analysis of cytosolic proteins indicated that growth in Tween 80 produced a higher stress state and increased relative abundance of three cell envelope proteinases (CEPs) (including PrtP and Dumpy), amongst over 230 differentially expressed proteins.

中文翻译：

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耐酸、持久的切达干酪分离物 Lactaseibacillus paracasei GCRL163 的特性

硬质奶酪的独特风味主要归因于非发酵乳酸菌 (NSLAB) 的活性，该乳酸菌在食用乳糖后的成熟过程中主导着奶酪基质。了解不同的 NSLAB 菌株如何生存、竞争和清除可用营养素对于选择菌株作为可能影响产品特性的潜在辅助起始剂至关重要。在澳大利亚切达干酪的 63 周成熟期的不同阶段占主导地位的三种副干酪乳酸杆菌分离株具有相同的分子生物型。他们共享许多表型特征，包括耐盐性、最佳生长温度、N-乙酰氨基葡萄糖和 N-乙酰半乳糖胺的生长以及 D-核糖的延迟生长，由于细菌自溶，奶酪中可能存在碳源。然而，菌株 124 和 163（后来命名为 GCRL163）在低 pH 值下存活时间更长，并在 D-塔格糖和 D-甘露醇上生长，将这种表型与菌株 122 区分开来。在高浓度的 L-亮氨酸和其他氨基酸中，GCRL163 产生并随后消耗乳酸，形成乙酸和甲酸，并在长期培养中证明丙酮酸代谢中间体的时间积累。菌株 GCRL163 在 Tween 80-胰蛋白胨肉汤中生长，本研究中筛选的所有干酪乳杆菌群乳品分离株均不具有这一特征。在这种培养基中加入柠檬酸盐会刺激 GCRL163 的生长高于单独的柠檬酸盐，表明柠檬酸盐和吐温 80 的共代谢。