Deactivation Kinetics of Nitrile Hydratase in Free Resting Cells

Nitrile hydratase (NHase) is an important industrial enzyme used for acrylamide production from acrylonitrile.The deactivation kinetics of NHases in free resting cells of Rhodococcus sp.was presented based on a bi-steady state assumption.Effects of hydration temperature,product concentration and substrate concentration on NHase deactivation were investigated experimentally and correlated with a first order deactivation kinetics.The results showed that the hydration temperature and product concentration were major factors governing the deactivation of NHases under substrate-feeding conditions.When acrylamide concentration was higher than 250 g·L1,the deactivation of NHases became serious and the bi-steady state assumption was not applicable.When the hydration temperature was controlled at a relatively higher level such as 28°C,the total deactivation rate constant was about 2.8-fold of that at 20°C.

Seasonal Variation in Abundance and Species Composition of a Planktonic Diatom Assemblage Including Viable Cells on the Bottom in Matsushima Bay, Northeastern Japan

Seasonal variation in abundance and species composition of a planktonic diatom assemblage distributed in the water column and also settled on the bottom was investigated for the shallow coastal water in Matsushima Bay on the Pacific coast of northeastern Japan during the period from October 1999 to September 2000. A spring bloom of diatoms began in April when nutrient concentrations started to increase, indicating the importance of nutrients. Viable cells of Skeletonema costatum and Thalassiosira spp., which were the dominant species in the water column throughout the year, were also always abundant in the bottom sediment. Both populations in the water column and on the bottom fluctuated essentially in parallel.For the planktonic diatoms in shallow coastal waters to maintain their vegetative populations in the water column, it would be advantageous for them to have a seeding population of viable cells on the bottom that are easily resuspended into the upper photic layer.

Microbial transformation of lovastatin by Beauveria bassiana

Microbial transformation of lovastatin(1)by resting cells of a filamentous fungus,Beauveria bassiana AS 3.4270,yielded five metabolites(2-6),which were unambiguously characterized by various spectroscopic data analyses.The occurred reactions included hydroxyla-tion,lactone hydrolysis and methylation.The inhibitory effects of all metabolites on the 3-hydroxy-3-methylglutaryl coenzyme A(HMG-CoA)reductase were evaluated.Of the five compounds,4 ex hibited comparable inhibitory effect to lovastatin on the HMG-CoA reductase with ICso value of 2.2μM,and inhibitory rate of 81.4%.