Hideo Tsuruga

β-Mannanase and xylanase of Bacillus subtilis 5H active for bleaching of crude pulp

A bacterial strain, 5H was isolated as a utilizer of locust bean gum (LBG) from soil in Chiang Mai, Thailand, and identified as Bacillus subtilis. Strain 5H produced β-mannanase and xylanase, which were purified to homogeneity from the culture filtrate by ion exchange chromatography and gel filtration. The molecular weights of β-mannanase and xylanase were found to be 37,000 and 26,000 by sodium dodecyl sulfonate polyacrylamide gel electrophoresis, respectively. The enzymatic properties of both were determined. Mannanase hydrolyzed LBG and konjak mannan endwisely, to a final hydrolytic degree of 15% and 21%, respectively, and the main products of both were disaccharides. Xylanase hydrolyzed larch wood xylan and oat spelt xylan, to a final hydrolytic degree of 19% and 38%, respectively, and produced mainly disaccharides. This culture filtrate (4.9 units/ml β-mannanase and 3.2 units/ml xylanase), a mixture of purified β-mannanase (4.9 units/ml) and xylanase (3.2 units/ml), and purified xylanase (3.2 units/ml) bleached crude paper pulp from 30% to 38% brightness, and xylanase was found to be more effective for paper-bleaching than β-mannanase.

Microbial production and vaporization of mono-(2-ethylhexyl) phthalate from di-(2-ethylhexyl) phthalate by microorganisms inside houses.

Laboratory workers were bothered by an irritation that caused coughing during the cultivation of microorganisms that degraded di-(2-ethylhexyl) phthalate (DEHP). The authors found that mono-(2-ethylhexyl) phthalate (MEHP), a known cause of asthma, was released during the degradation of DEHP. At its highest production and vaporization rate, the amount was almost equal to that of the DEHP starting material. It appeared that transport into the atmosphere depended on its adsorption on dust particles. The authors attempted to cultivate several microorganisms from house materials, especially those composed of rotting polyvinyl chloride. And microorganisms produced MEHP in the culture medium. In addition, MEHP was produced from DEHP by several stock microorganisms. Thus, MEHP could easily be produced from DEHP by microorganisms in the environment. In Japan, there are many cases of asthma with unknown causes. If MEHP is one of causes, then preventive measures against some cases of asthma could be taken.

FORCED CONVECTION HEAT TRANSFER FROM SUBMERGED SURFACE TO LIQUID HELIUM

Heat transfer from a vertical copper surface submerged in circulating liquid helium in a dewar was studied experimentally. Heat transfer increased with the increase of velocity of liquid helium in convective heat transfer region. The data were correlated with an empirical equation as Nusselt number vs. Reynolds number. The peak nucleate boiling heat flux decreased with increasing flow velocity, whereas minimum film boiling heat flux increased with circulating flow velocity.