Consume Pattern And Necessary Pattern Of Streptococcus Thermophilus ST7

As an important strain of direct investment type of starter cultures, Streptococcus thermophilus is widely applied to the production of fermented dairy products. High density cultivation is one of key technology during the preparation of direct investment type of starter cultures. The lack of basic theory on nutritional requirements and metabolic mechanisms of Streptococcus thermophilus, especially the lack of amino acid metabolic mechanisms, makes the research on nutrients screening random and blindness. In order to solve these technical problems fundamentally, we must begin with the basic theory research of nutrient metabolism involved in Streptococcus thermophilus high density cultivation. The theoretical interpretation about necessary pattern, consume pattern, metabolic regularity of Streptococcus thermophilus and links with the whole physical condition in cells, will provide scientific theoretical guidance on medium design during high density cultivation process of Streptococcus thermophilus. This paper mainly focus on preliminary study in amino acid necessary and consumption pattern of Streptococcus thermophilus in the cultivating process, aiming to lay foundation on follow-up study.Using a single amino acid omissions technology, this paper studies the effect of20kinds of amino acids on Streptococcus thermophilus ST7growth. Using amino acid analysis technology, this paper studies the consumption pattern of20kinds of amino acids along with the change of growth rate during Streptococcus thermophilus ST7growth. Using cell disruption and amino acid analysis technology, this paper studies the necessary pattern of amino acids along with the change of growth rate during Streptococcus thermophilus ST7growth.After analysis the growth characteristic of Streptococcus thermophilus ST7, this research study the effect of20kinds of amino acids on Streptococcus thermophilus ST7growth with a single amino acid omissions technology. The results prove that arginine, alanine, serine, histidine, leucine, valine, tryptophan, lysine, phenylalanine, tyrosine and threonine is the essential amino acid during the growth of Streptococcus thermophilus ST7, the lack of Glutamic acid, methionine, glutamine, proline, glycine and cysteine almost had no significant effect on the growth of Streptococcus thermophilus ST7, aspartic acid, asparagine and isoleucine hinders the growth of Streptococcus thermophilus ST7. This study also finds that branched chain amino acids, fatty hydrocarbon chains of amino acids have large effect on the growth of Streptococcus thermophilus ST7.The consume pattern of20kinds of amino acids along with the change of growth rate during Streptococcus thermophilus ST7growth shows that arginine makes the largest consumption (13.75mmol gdw-1), the second is the consumption of glutamic acid and glutamine (consumption of glutamic acid is12.42mmol gdw-1, consumption of glutamine is12.15mmol gdw"1). The consumption of aspartic acid, asparagine, serine, alanine, threonine, glycine, lysine, leucine, methionine, valine, phenylalanine and isoleucine followed (consumption ranging from5.25mmol gdw-1to1.2mmol gdw-1). Arginine, glutamine and asparagine are the major source of nitrogen consumption. From the experimental results we can obtain that arginine plays an important role in reducing nitrogen loss. Most of arginine consumption will be converted into other amino acids under the low growth rate condition.The necessary pattern of amino acids along with the change of growth rate during Streptococcus thermophilus ST7growth shows that during the whole growth, the demand of arginine (2.04mmol gdw-1) is significantly higher than other amino acids. Demand of aspartic acid, alanine, glycine, glutamic acid, lysine, leucine, isoleucine, valine, threonine, serine, proline and tyrosine followed (ranging from1.98mmol gdw-1to0.76mmol gdw"1). Phenylalanine, methionine, histidine, tryptophan and cysteine has a minimal demand (demand of these amino acids is less than0.58mmol gdw-1)From the analysis results of consume pattern and necessary pattern of20kinds of amino acids along with the change of growth rate during Streptococcus thermophilus ST7growth, we can conclude that arginine is the most important amino acid to Streptococcus thermophilus ST7growth. Aspartic acid and glutamic acid also play a very important role in Streptococcus thermophilus ST7growth. Consumption of arginine. aspartic acid, glutamic acid, serine, threonine and cysteine is apparently about3-6times higher than biosynthesis of demand, which illustrates that there exists nitrogen waste during Streptococcus thermophilus ST7growth.