Abstract: An industrial process for producing hydroxyaldehydes efficiently, by solving the problems of conventional DERA, such as low stability against aldehydes, low catalytic activity for aldol condensation, and the difficulty of controlling the number of acetaldehyde molecules to be condensed, is provided. According to the process, aldol condensation of a substituted or unsubstituted aliphatic aldehyde compound having 2 to 6 carbon atoms with acetaldehyde is conducted by using D-2-deoxyribose-5-phosphate aldolase which is highly stable against aldehydes and has high catalytic activity for aldol condensation, whereby a hydroxyaldehyde compound having the number of carbon atoms increased by two or four can be produced.

Abstract: An industrial process for producing hydroxyaldehydes efficiently, by solving the problems of conventional DERA, such as low stability against aldehydes, low catalytic activity for aldol condensation, and the difficulty of controlling the number of acetaldehyde molecules to be condensed, is provided. According to the process, aldol condensation of a substituted or unsubstituted aliphatic aldehyde compound having 2 to 6 carbon atoms with acetaldehyde is conducted by using D-2-deoxyribose-5-phosphate aldolase which is highly stable against aldehydes and has high catalytic activity for aldol condensation, whereby a hydroxyaldehyde compound having the number of carbon atoms increased by two or four can be produced.

Abstract: The preparation of an L-amino acid, particularly valine, leucine, isoleucine, alanine and phenylalanine, from the corresponding .alpha.-keto carboxylic acid by bacterial fermentation in the presence of ammonium ions is carried out with the aid of thermophilic Bacillus strains at temperatures above 45.degree. C., in particular above 60.degree. C. Bacillus strains DSM 406, 452, 461, 42, 463, 465 and 466 are particularly suitable for this purpose. The greater solubility of the amino acid at the elevated fermentation temperature permits the separation out of the amino acid from the reaction mixture simply by cooling, whereafter the depleted reaction mixture can be pumped back into the fermenter. Especially favorable yields are achieved by supplying oxygen to the fermenter to an amount of less than about 20% dissolved oxygen.

Abstract: Leucine dehydrogenase is disclosed which retains 80% or more of the activity even after it is incubated in a buffer solution at about 70.degree. C. for 10 minutes, as compared to the activity prior to incubation. A process for producing a heat resistant leucine dehydrogenase is also disclosed. The process comprises culturing a microorganism having an optimum growth temperature of 50.degree. to 85.degree. C. and harvesting the leucine dehydrogenase from the culture and a composition of assaying for leucine aminopeptidase (LAP) comprising the heat resistant leucine dehydrogenase.The leucine dehydrogenase can be stored for a long period of time and thus very effective for investigations in biochemistry, food analysis and clinical test. Further the composition provides extremely easy assay for the LAP activity in high accuracy with good reproducibility which is an important item in clinical test.