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

Abstract

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.

Metabolic profiles of cysteine, methionine, glutamate, glutamine, arginine, aspartate, asparagine, alanine and glutathione in Streptococcus thermophilus during pH-controlled batch fermentations

“…The results of the current study showed that ST-MZ-2 does not have the ability to synthesize arginine through a de novo pathway. The expression levels of astB and ADC , and changes in arginine concentration is consistent with our previous research results 3,12 . N-acetyl-ornithine has been found to protect against osmotic stress in some microorganisms 20 , but whether N-acetyl-ornithine helps ST-MZ-2 resist osmotic stress needs further study.…”

“…Previous studies have shown that the consumption of AAs exceeded the amounts necessary for the growth of L. lactis and S. thermophilus , implying a significant overconsumption of AAs 3,12,21 . The findings obtained in the present study indicated that the overconsumption of AAs might be mainly attributed to the production of large amounts of end-products and intermediates of the AA metabolism.…”

“…The expression levels of their synthesis genes and changes of their concentrations indicated that aspartate was not found at sufficient amounts for their synthesis at the stationary phase. A previous study showed that aspartate was hardly consumed and should thus be produced from asparagine 12 . The overconsumption of asparagine might be necessary to maintain an effective transfer of amino groups.…”

“…However, the reasons for the functions of the abovementioned AAs and their metabolic pathways in S. thermophilus have not been fully studied. Our previous study showed that the consumption of some AAs notably exceeds the necessary amounts for the growth of S. thermophilus , implying a significant overconsumption of AAs 3,12 . Based on our results and those of previous studies, we proposed the following series of questions: (i) How are these AAs metabolized in S. thermophilus ?…”

Influence of arginine on the growth, arginine metabolism and amino acid consumption profiles ofStreptococcus thermophilusT1C2 in controlled pH batch fermentations

“…In addition, the previous results showed that nitrogen waste may be primarily attributed to the excessive consumption of arginine (Hong et al . ). Based on our results and on previous reports, a series of questions were proposed including (i) could arginine stimulate the growth of Strep.…”