Bacteria enzyme production

In this chapter we describe the use of pea seeds to express the bacterial enzyme a-amylase. Bacterial exoenzymes like the heat stable a-amylase from Bacillus licheni-formis are important for starch hydrolysis in the food industry. The enzymatic properties of a-amylase are well understood [13,14], it is one of the most thermostable enzymes in nature and it is the most commonly used enzyme in biotechnological processes. Although fermentation in bacteria allows highly efficient enzyme production, plant-based synthesis allows in situ enzymatic activity to degrade endogenous reserve starch, as shown in experiments with non-crop plants performed under greenhouse conditions [12,15]. Finally, the quantitative and sensitive detection of a-amylase activ-... 

New biocatalysts (genetically modified bacteria) could break up cellulose/ hemicellulose, but it is necessary, on one hand, to decrease the cost of enzyme production and, on the other hand, to improve reactor and process technology,... 

Bacteria represent a promising source for the production of industrial enzymes. Bacterial cellulases are an especialfy interesting case in point. Many thermophilic bacterial species produce cellulases that are stable and active at high temperature, resistant to proteolytic attack, and stable to mechanical and chemical denaturation. However, cellulase productivities in bacteria are notoriously low compared to other microbial sources. In this paper bacterial enzyme production systems will be discussed with a focus on comparisons of the productivities of known bacterial cellulase producers. In an attempt to draw conclusions concerning the regulation of cellulase synthesis in bacterial systems, a tentative model for regulation in Acidothennus cellulofyticus has been developed. 

When grown in alkaline media, certain species of lactic acid bacteria decrease production of LDH, resulting in increased formation of formate, acetate, and ethanol as end products. This phenomenon has been observed in S. faecalis subsp. liquefaciens (Gunsalus and Niven 1942), Streptococcus durans, S. thermophilus, (Platt and Foster 1958), and Lactobacillus bulgaricus (Rhee and Pack 1980). Data of Rhee and Pack (1980) indicate that a phosphoroclastic split of pyruvate occurs under alkaline conditions to yield ATP. The enzymes involved in this reaction (pyruvate formate-lyase and acetate kinase) require alkaline conditions for optimum activity. A shift from homo- to heterofermentation because of increased pH has not been observed for Group N streptococci. 

Rowe, M.T., Johnston, D.E., Kilpatrick, D.J., Dunstall, G., Murphy, R.J. 1990. Growth and extracellular enzyme production by psychrotrophic bacteria in raw milk stored at a low temperature. Milchwissenschaft 45, 495 199. 

Cellulases are found in fungi and bacteria. Of commercial interest are fungal enzymes from Aspergillus or Trichoderma and a few bacterial enzymes. They are either used as a multicomponent, which contain all enzyme types and are found in Trichoderma reesei (Hypocrea jecorina), or as a monocomponent enzyme product, which consists of only one of the three types of enzymes. The multicomponent enzyme preparations can be produced from a selected cellulose overproducing strain of the wild-type organism, whereas the monocomponent cellulases are mainly produced in recombinant production systems. 

The use of enzymes in drinking-water treatment has several advantages over the use of whole bacteria. Enzymes often have high specificities for substrate, so there is better control over the compound removed and the product produced. The enzyme concentration in the water is controlled by the plant operator. Thus there is no dependence on the growth rate of the bacteria. This can be particularly important when the compound targeted for removal appears only sporadically in the raw water, such as taste and odor compounds. Bacteria require an incubation time to acclimate to the substrate and grow, but enzymes may be added as needs require. 

An iniponani propeny of enzymes is that they are specific that is. one enzyme can usually catalyze only one type of reaction. For example, a protease hydrolyzes only bonds between specific amino acids in proteins, an amylase works on bonds between glucose molecules in starch, and lipa.se attacks fats, degrading them to fatty acids and glycerol, Con.sequently, unwanted products are easily controlled in enzyme-catalyzed reactions. Enzymes are produced only by living organisms, and commercial enzymes are generally produced by bacteria. Enzymes usually work (i.e., catalyze reactions) under... 

Yeast fatty acid S5mthase has an ttgPg structure where the 208-kDa a subunit contains the ACP-like site, the active site -SH, and three catalytic activities. The 220-kDa P subunit has five catalytic activities. The yeast enzyme contains the FMN thought to act as FMNHj in the second reduction step. As in bacteria, the products of the complex are molecules of acyl-CoA of chain... 

---