Effect of nitrogen source and nitrogen concentration on the production of pyruvate by Torulopsis glabrata

The effect of nitrogen sources including yeast extract, peptone, soybean hy drolyzate and some inorganic nitrogen sources, as well as the nitrogen conc entration on the fermentative production of pyruvate by Torulopsis glabrata WSPT-IP12 was investigated. The addition of yeast extract greatly inhibite d pyruvate accumulation, while peptone was shown to be the most favorable n itrogen source. In flask culture, 15 g l(-1) peptone was needed to consume 80 g l(-1) glucose with 23.4 g l(-1) of pyruvate accumulated. Pyruvate prod uction was markedly dependent on the ratio of carbon to nitrogen (C:N), its production was improved by increasing the concentration of glucose and pep tone proportionally and reduced by exclusively increasing the glucose conce ntration. In a glucose fed-batch culture, cell growth and pyruvate producti on slowed after 28 h. However, cell growth and pyruvate production recovere d after further nitrogen, in the form of peptone and ammonium sulfate, was added to the culture. A final concentration of pyruvate of 54.5 g l(-1) was achieved at 64 h (yield to glucose consumed of 0.471 g g(-1)). By using aq ueous ammonia instead of potassium hydroxide for pH control, 57.3 g l(-1) p yruvate with a yield of 0.498 g g(-1) was produced by 55 h. This result fur ther indicates that nitrogen level plays an important role in the productio n of pyruvate. (C) 2000 Elsevier Science B.V. All rights reserved.