Applications of high-hydrostatic-pressure processing on microbial enzymes

Microbial enzymes find immense applications as biocatalysts or processing aids in food, agricultural, chemical, and pharmaceutical production. While high-hydrostatic-pressure processing (HPP) is one of the most widely used nonthermal techniques in the food industry to inactivate food pathogens, especially vegetative cells, the current literature has also documented that HPP, at certain pressure, temperature, and time combinations, can affect the stability and enzyme-substrate catalytic activity of enzymes. Effects of HPP on eight major types of microbial enzymes, i.e., α-amylase, glucoamylase, β-galactosidase, cellulase, xylanase, pectinase, lipase, and protease, are discussed in this book chapter. The effects of HPP parameters (e.g., pressure intensity, temperature, operating in the presence of aqueous or organic media or compressed gases) on enzyme stability and catalytic activity are also summarized. The effect of HPP on enzyme stability and enzyme-substrate reactions appears to be enzyme-dependent and affected by the enzyme source and preparation, the presence of other concomitant components (e.g., salt metal ions), the type of substrate selected, and the presence of enzyme cofactors and inhibitors. In addition, enzyme immobilization or protein engineering techniques applied to microbial enzymes prior to HPP may have additive or synergistic effects on enzyme stability and catalytic activity. The studies reviewed in this chapter suggest that HPP has great potential for enzyme enhancement during biocatalysis, thereby increasing the catalytic efficiency of microbial enzymes and the targeted end-product yield.