Microbial enzymes: industrial progress in 21st century

Abstract

Microbes have been utilized since ancient human civilization with first reported commercial application of yeast to produce alcoholic beverages from barley by the Babylonians and Sumerians as early as 6000 BC. The microbial enzymes have gained recognition globally for their widespread uses in various sectors of industries, e.g., food, agriculture, chemicals, medicine, and energy. Enzyme mediated processes are rapidly gaining interest because of reduced process time, intake of low energy input, cost effective, nontoxic and eco-friendly characteristics (Li et al. 2012 ; Choi et al. 2015 ). Moreover, with the advent of recombinant DNA technology and protein engineering a microbe can be manipulated and cultured in large quantities to meet increased demand (Liu et al. 2013 ). Associated driving factors that motivate the use of microbial enzymes in industrial applications are increasing demand of consumer goods, need of cost reduction, natural resources depletion, and environmental safety (Choi et al. 2015 ). Global market for industrial enzymes was estimated about $4.2 billion in 2014 and expected to develop at a compound annual growth rate (CAGR) of approximately 7 % over the period from 2015 to 2020 to reach nearly $6.2 billion ( 2015b : Industrial Enzyme Market). Enzymes are biological molecules, proteinaceous in nature with the exception of catalytic RNA molecules (ribozymes), and act as catalyst to support almost all of the chemical reactions required to sustain life (Cech and Bass 1986 ). Enzymes are highly specific; only accelerate the rate of particular reaction by lowering the activation energy without undergoing any permanent change in them, and therefore, are vital biomolecules that support life (Fersht 1985 ; Piccolino 2000 ; Aldridge 2013 ). They require typically milder condition of temperature and pressure for catalyzing reactions, and are used as an alternative to hazardous chemical pollutant owing to their biodegradable and nontoxic nature (Mojsov 2011 ; Illanes et al. 2012 ; Choi et al. 2015 ). In addition to advantages of enzymes over conventional methods, there are some drawbacks of using enzymes in healthcare and other industries. For many mammalian enzymes, 37°C and 7.4 are the optimal temperature and pH, respectively, and their activity is highly sensitive to any change in these parameters. Higher temperature (>40°C), and a large deviation from the physiological pH (7.4) lead to their denaturation, which limits the use of these macromolecules in non-physiological conditions. Additionally, they are susceptible to substrate or product inhibition and their products may cause allergic reactions. The high cost of isolation and purification of enzymes and their difficult recovery for subsequent reuse may discourage their use (Johannes et al. 2006 ).