Kazuo Uchida

Studies on pH of shoyu koji. Part I. Relationship between pH and citric acid content in shoyu koji.

醤油麹のpHに及ぼすクエン酸量の影響,麹菌のクエン酸代謝について調べ,次の結果を得た. (1) 麹のクエン酸量は麹pHと負の相関関係にあった. (2) 麹のクエン酸量は散水量,培養湿度,菌株によって大きく異なった.クエン酸は低散水量,低温培養麹ではクエン酸が生成,蓄積され,高散水量,高温培養麹では消費,減少する傾向があった. (3) トレーサー実験より,A. oryzaeを使用した100%散水,23°C培養で,添加したリンゴ酸,ピルビン酸よりクエン酸が生成され,添加したクエン酸は消費されず麹中にクエン酸が蓄積されることが示された.しかし,A. sojaeを使用すると同条件で,添加したクエン酸がわずかに消費されておりA. oryzaeと若干異なっていた.一方,180%散水,33°C培養では両菌株ともに添加したクエン酸は消費,減少した. (4) クエン酸代謝関遵酵素活性はA. oryzae,A. sojaeともに,100%散水,23°C培養麹では180%散水33°C培養麹に比較してクエン酸シンターゼ活性が高く,アコニターゼ活性が低い傾向にありクエン酸の生成,消費と関連していた.

Studies on 5′-Nucleotidase-Lacking Mutants Derived from Bacillus subtilis: Part I. Derivation of Mutants from an Adenine Auxotroph and their Some Properties

Two 5′-nucleotidase-lacking mutants, R–42 and A–1, were derived from an adenine-requiring mutant, B. subtilis 1145–2–83, which has productivity of both inosine and hypoxanthine. Strain A–1 accumulated 5′-IMP as well as inosine and hypoxanthine, and strain R–42 accumulated 5′-IMP and 5′-GMP as well as inosine and hypoxanthine in their culture fluids. These mutants responded to either adenine or adenosine, but did not to 5′-AMP. This fact suggests that adenine or adenosine may be incorporated into the cells, but 5′-AMP may neither be incorporated into the cells nor be degraded during culture. 5′-GMP was converted to 5′-IMP, and 5′-AMP was phosphrylated to ADP in the growing culture of strain A–1.

Studies on 5'-Nucleotidase-Lacking Mutants Dewrived from Bacillus subtilis:Part II. The Influence of the Loss of 5'-IMP-Dephosphoirylating Activity on the Extracellular Accumulation of Hypoxanthine Derivatives in an Adenine-Requiring Mutant

For the purpose of effective accumulation of 5′-MMP, mutants, whose 5′-IMP-dephosphorylating activities were lower than that of strain A-1 of B. subtilis capable of accumulating a small amount of 5′-IMP as well as inosine and hypoxanthine, were derived from inosine-producing strain 1145-2-83 and strain A-1.As a result, several mutants different from one another in the level of 5′-IMP-dephos- phorylating activity were isolated. Any of them did not acquire high ability to accumulate 5′-IMP. The more the mutants lost 5′-IMP-dephosphorylating activity, the less they accumulated extracellular inosine. The loss of nucleotide-dephosphorylating activity in the adenine-requiring mutants resulted in a remarkable increase in the amount of adenine required. The accumulation of 5′-IMP was not repressed by the addition of adenine at the concentration enough to repress accumulation of inosine.