Recent Advances in Microbial Raw Starch Degrading Enzymes

Abstract

Raw starch degrading enzymes (RSDE) refer to enzymes that can directly degrade raw starch granules below the gelatinization temperature of starch. These promising enzymes can significantly reduce energy and simplify the process in starch industry. RSDE are ubiquitous and produced by plants, animals, and microorganisms. However, microbial sources are the most preferred one for large-scale production. During the past few decades, RSDE have been studied extensively. This paper reviews the recent development in the production, purification, properties, and application of microbial RSDE. This is the first review on microbial RSDE to date.

Purification and Characterization of α-Amylase from Bacillus subtilis Isolated from Cassava Processing Sites

“…Enhancement of amylase activity by metallic ions might be due to their ability interact with negatively charged amino acid residues such as aspartic and glutamic acid [42], thereby stabilizing and maintaining the enzyme conformation. Researchers have reported inhibition of amylase activity by Ag + , Hg 2+ , Cd 2+ , Cu 2+ , Pb 2+ , Fe 2+ , Ni 2+ , Mn 2+ and Zn 2+ ions [10,37,43]. The result obtained from this study agrees with the findings of Igarashi et al [44] who reported strong inhibition 100% (0% relative activity) of Hg 2+ ions on alpha amylase from Bacillus specie.…”

Starch and Microbial α-Amylases: From Concepts to Biotechnological Applications

“…Also, the pH values were reported to serve as an indicator of the initiation and end of enzyme synthesis (Friedrich et al, 1989) because the change in pH affects -amylase stability in the medium (Calamai et al, 2005). It is worth noting that the -amylase active site consists of a large number of charged groups (Lawson et al, 1994;Strokopytov et al, 1996;Uitdehaag et al, 1999) which explain the fact that most -amylases had optimum pH in the acidic to neutral range (Bozic et al, 2011;Pandey et al, 2000;Sun et al, 2010).…”

“…The used methods to purify amylases can vary considerably, but most purification protocols involve a series of steps (Sun et al, 2010). The choice of purification protocol naturally depends on the intended use, the highest purity usually being required for basic purposes in which even separation of isozymes may be important.…”

Construction of Amylolytic Industrial Strains of Saccharomyces cerevisiae for Improved Ethanol Production from Raw Starch

“…Raw starch degrading enzymes (RSDE) refer to amylases that can hydrolyze raw starch directly, without an additional high energy-consuming process, such as gelatinization (Shigechi et al, 2004). Many genes of filamentous fungi and yeasts that encode for RSDE have been previously expressed in S. cerevisiae (Sun et al, 2010). A recombinant S. cerevisiae that could synthesize and secrete RSDE efficiently might be used to simplify the process and to reduce the costs of ethanol production from raw starch.…”

“…The additional multicopy rDNA-integration of the GA1 or AMY genes can be correlated with the high-level expression of the corresponding genes (Nieto et al, 1999;Choi et al, 2002). The increase in activities of glucoamylase in addition to α-amylase is necessary for the more complete degradation of raw starch into glucose units, and consequently, more efficient ethanol production (Shigechi et al, 2004;Sun et al, 2010). Time courses of the cell growth and activities of α -amylase and glucoamylase from ATCC 9763/YIpδAGSAδ /YIpAG2rD were compared with those of the parental strain.…”