Short communication: Evaluation of amino acid consumption and necessary profiles of Streptococcus thermophilus T1C2 in controlled pH batch fermentations.

The objective of the present study was to elucidate the relationship between amino acid consumption and necessary profiles of Streptococcus thermophilus T1C2 to guide the design of media for high-cell-density culture. The amino acid consumption and necessary patterns of S. thermophilus T1C2 were investigated in the complete chemically defined medium. For amino acid consumption profiles throughout the growth of S. thermophilus T1C2, the most abundantly consumed amino acids were Gln and Arg, which accounted for 19 and 20% of total amino acids consumed, respectively. Asparagine, Thr, Ser, Ala, Val, Met, Leu, and Lys, consumptions of which ranged from 3 to 10% of total amino acids consumed, were the second most intensively consumed amino acids. For necessary amino acid patterns, the amount of Cys, which counted for 11% of total amino acids needed, was significantly higher than the amounts required for other amino acids in growth of S. thermophilus T1C2. The necessary amounts of Asp, Asn, Glu, Gln, Arg, Ala, Met, and Tyr ranked second, ranging from 5 to 8% of total amino acids needed. Compared with necessary amounts, the consumption of Asn, Thr, Ser, Gln, Arg, Ala, Val, Leu, Lys, His, and Phe exceeded the necessary amounts for growth of S. thermophilus T1C2 remarkably. Consumption of Gly, Met, Ile, Trp, and Pro was slightly higher than the necessary amounts. Consumption of Asp, Glu, Tyr, and Cys was lower than the necessary amounts. The overall consumption of amino acids exceeded the required amount for growth of S. thermophilus T1C2 almost 2.43 times, which implied a significant nitrogen wasting.