エタノール, 酢酸およびアセトアルデヒドを炭素源とするCandida utilisの培養特性

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An ethanol-, acetic acid-, and acetaldehyde-utilizing yeast, MG-1,was isolated and identified as Candida utilis on the basis of its biological characteristics and coenzyme Q system. Batch cultures of C.utilis MG-1 were carried out with ethanol, acetic acid, or acetaldehyde as a carbon source. Optimum concentrations of substrates were below 0.3 wt% for ethanol, below 0.05 wt% for acetic acid, and below 0.03 wt% for acetaldehyde. Optimum temperature was 36-38℃, and optimum pH was 3.5-4.5 for growth with these substrates. Continuous cultures of C.utilis MG-1 were carried out with ethanol, acetic acid, or acetaldehyde as a carbon source. Cell yield increased slightly with dilution rate up to the practical dilution rate (D_p, hr^<-1>), and the contents of crude protein and nucleic acids also increased, while the content of amino acids remained constant. The contents of crude protein and nucleic acids decreased in parallel with the increase of temperature but the content of amino acids was constant at 28-38℃. At a constant feed concentration of 5-60 grams of ethanol per liter, the D_p was approximately 0.50 hr^<-1>, the cell yield was approximately 80 wt%, and the content of crude protein was approximately 58 wt%. At a constant feed concentration of 10-60 grams of acetic acid per liter, the cell yield was approximately 40 wt%, and the content of crude protein was approximately 59 wt%. The D_p decreased in parallel with the increase of feed concentration of acetic acid, from approximately 0.43 hr^<-1> at 1.0 wt% of acetic acid to approximately 0.30 hr^<-1> at 6.0 wt%. At the constant feed concentration of 10 grams per liter of acetaldehyde, the D_p was approximately 0.18 hr^<-1>, the cell yield was approximately 55 wt%, and the content of crude protein was approximately 55 wt%. The concentration of cells and the productivity of cells increased in parallel with the dilution rate and the feed concentration of the carbon source. At the feed concentration of 6.0 wt% of ethanol, the concentration of cells was approximately 4.8 wt%, and the maximum productivity of cells was approximately 24 g/l・hr. At the constant feed concentration of 6.0 wt% of acetic acid, the concentration of cells was 2.4 wt%, and the maximum productivity of cells was approximately 7 g/l・hr. Of the three substrates, ethanol was the best for C.utilis MG-1 with respect to growth rate, cell yield, oxygen requirement, and heat of fermentation.
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エタノール, 酢酸およびアセトアルデヒドを炭素源とするCandida utilisの培養特性

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