Tetsuro Fukase

Stimulation of protease production byAspergillus oryzae with oils in continuous culture

SummaryThe effect of soy sauce oil and various other oils on protease production by Aspergillus oryzae NISL 1913 was studied in chemostat cultures (dilution rate=0.02 h−1). Soy sauce oil was consumed as a carbon source by the cells and also accelerated protease production. When soy sauce oil was used as sole carbon source, the specific protease production rate was 2.89 protease units·(mg dry weight of mycelium)−1·h−1, which was threefold higher than that with starch. The specific protease production rate with linoleic acid, oleic acid, Tween 80 and soybean oil exhibited similar values to that with soy sauce oil but the fatty acids with carbon chains shorter than six, such as caproic acid and acetic acid, did not stimulate protease production. The oils did not cause an increase in other exocellular enzymes such as α-amylase, indicating that the protease production was selectively stimulated by the oils.

Isolation of microorganisms that lyse filamentous bacteria and characterization of the lytic substance secreted by Bacillus polymyxa

Microorganisms capable of lysing filamentous bacteria were isolated from activated sludge by screening for their ability to form plaques on an agar plate seeded with cells of Sphaerotilus natans. The supernatant obtained by culturing of these microorganisms lysed filamentous bacteria in a liquid culture. After purification using column chromatography followed by anion-exchange, gel-filtration and hydroxyapatite chromatography, the lytic substance produced by of B. polymyxa showed the highest lytic activity in all of screened bacteria. However, a specific band representing the substance responsible for the lytic activity could not be observed on SDS-polyacrylamide gel. In addition, the lytic substance could not be rendered inactive by various enzyme denaturing treatments. The substance has properties similar to those of a biosurfactant that is often produced by B. subtilis.

Cloning and sequence analysis of an esterase gene from Pseudomonas sp. KWI-56.

The gene encoding an esterase from Pseudomonas sp. KWI-56 was cloned and sequenced. The nucleotide sequence contained an open reading frame encoding a polypeptide comprising 262 amino acids, whose molecular weight agreed well with the value obtained by SDS-PAGE. Comparison of the amino acid sequence with those of the other homologous enzymes suggested that Ser-92 and His-24l might be included in the catalytic triad.

Hyperproduction of Thermostable Lipase by Genetically Engineered Pseudomonas Species

One Pseudomonas species was isolated, and named KWI-56, which produced an extracellular thermostable lipase. More than 90% of the enzyme activity remained after 24 hours’ heat treatment at 60 °C [1].