Microbial enzymes, importance

Metabolic reactions in the liver and the small intestine are well documented [24]. However, only sparse information is available on drug metabolism in the eolon. Drug metabolism in the colon can be brought about by the host enzymes in the epithelial cells or by the microbial enzymes in the gut flora. Metabolie aetivities in the wall of the colon can be attributed to the eytochrome P450, esterases, amidases, and various transferases [25]. Reductive drug metabolism does not appear to be important at this site. 

Endogenous microbial enzymes are sometimes utilized to break down their parent cells, and thus extract valuable intracellular materials. For instance, in the production of yeast extract, cells are allowed to autolyse at about pH 5 and 55 0. Proteases are probably the most important class of enzymes involved in autolysis, although others such as glucanases, lipases and nucleases also have... 

As commercial interest grows in this area and more cost-effective microbial enzymes become available, it is inevitable that the application of enzymes in feed will further expand. In areas where feed enzymes are already widely applied, they have been acclaimed as the most important development in mono-gastric feeding this decade. 

In designing a microbial conversion process many important aspects require careful consideration, for example, the selection of a compound to be synthesized, a survey of available substrates, and the routes or reactions needed. Another point (the most important one) is to find microbial enzymes which are suitable for the processes designed, and to subsequently evaluate the enzyme s potential. Moreover, the discovery of a new enzyme or a new reaction provides a clue for designing a new microbial transformation process. To find microbial enzymes that are suitable as potent catalysts, the capabilities of well-known enzymes or reactions need to be reassessed, and novel microbial strains or enzymes need to be discovered. Screening may be one of the most efficient and successful ways of searching for new or suitable microbial enzymes. 

D-p-Hydroxyphenylglycine and its derivatives are important as side-chain precursors for semisynthetic penicillins and cepharosporines. Yamada and coworkers of our laboratory found that these amino acids can be efficiently prepared from the corresponding 5-monosubstituted hydantoins using the microbial enzyme D-hydantoinase [4]. 

An extension of this technology lead to the development of enzyme modified cheeses or EMC which are a very important product. The basic function of the process was to shorten the ripening time of a mature cheese without losing flavor. The potential financial gains are obvious. Young cheeses are subjected to a controlled lipolysis and proteolysis which is brought about by adding suitable microbial enzymes (8). After thermal inactivation of the enzymes, a pasty product is obtained which can have a flavor intensity of up to 20 times that of the mature cheese. 

For biotechnological synthesis, there is a superb database containing information on miaobial biocatalytic reactions and biodegradation pathways for primarily xenobiotic, chemical componnds. It is called the University of Minnesota Biocatalysis/Biodegradation Database (UM-BBD) at can be fonnd at http //nmbbd.ahc.umn.edu/search/index.html. The goal of the UM-BBD is to provide information on microbial enzyme-catalyzed reactions that are important for biotechnology. 

Since many enzymes have capacities to catalyze reactions with even unnatural substrates and to produce unnatural compounds, hybrid use of enzymes as biocatalysts with chemical synthesis can realize processes to produce useful substances with higher flexibility than processes with growing cells. Discovery of novel microbial enzymes with required specificity by screening is a key to the establishment of such a hybrid processes. Many successful achievements in Japan are observed in this unique field of biotechnology. Application of nitrile hydratase to production of acrylonitriles has proved that biocatalysts can be applied to production of commodity chemicals beyond the presumed limitation of fine chemicals. Discovery of the enzymatic reactions to produce trehalose from starch is an example that reveals the possibility of microbial screening or what remains undiscovered in the microbial world. The importance of developing new application is also crucial in this field as shown in the case of transglutaminase and alkaline cellulase. 

Publications giving the details of the actual development work in establishing industrial microbial enzyme processes are non-existent. It is, therefore, of interest to describe the development of a commercial enzyme process for one of the most important industrial enzymes, glucoamylase. Although there are many patents and publications on glucoamylase, nowhere has there previously been an attempt to gather together the available published and unpublished non-confidential information into a coherent report. 

The selection of an organism is the first important step in the development of any product. For microbial enzyme production several factors must be considered ... 

We successfully isolated and characterized new microbial enzymes from nature. Now, they have proved to be both scientifically and industrially important. Thus, the enrichment and acclimation culture techniques are two of the most active methods in the screening for microbial biocatalysts. 

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