Overcoming hydrolysis of raw corn starch under industrial conditions with Bacillus licheniformis ATCC 9945a α-amylase

Abstract

α-Amylase from Bacillus licheniformis ATCC 9945a (BliAmy) was proven to be very efficient in hydrolysis of granular starch below the temperature of gelatinization. By applying two-stage feeding strategy to achieve high-cell-density cultivation of Escherichia coli and extracellular production of BliAmy, total of 250.5 U/mL (i.e. 0.7 g/L) of enzyme was obtained. Thermostability of amylase was exploited to simplify purification. The hydrolysis of concentrated raw starch was optimized using response surface methodology. Regardless of raw starch concentration tested (20, 25, 30 %), BliAmy was very effective, achieving the final hydrolysis degree of 91 % for the hydrolysis of 30 % starch suspension after 24 h. The major A-type crystalline structure and amorphous domains of the starch granule were degraded at the same rates, while amylose-lipid complexes were not degraded. BliAmy presents interesting performances on highly concentrated solid starch and could be of value for starch-consuming industries while response surface methodology (RSM) could be efficiently applied for the optimization of the hydrolysis.

AmyZ1: a novel α-amylase from marine bacterium Pontibacillus sp. ZY with high activity toward raw starches

“…The starch-processing industries usually employ 20–30% concentration starch slurries as the starting substrates [16]. Thus, raw starch hydrolysis property of AmyZ1 was assayed under 30% starch concentration (Fig.…”

“…strain F10% (15% and 48 h)NMNM45NM[55] Geobacillus sp. 4j (Gs4j-amyA)45% (30% and 4 h)36% (30% and 4 h)0.5655.5[17] Bacillus amyloliquefaciens (BAA, Sigma)50% (30% and 4 h)15% (30% and 4 h)0.5655.5[17] Bacillus licheniformis (BLA, Sigma)50% (30% and 4 h)35% (30% and 4 h)0.5655.5[17] Bacillus licheniformis (BLA, Sigma)NM58% (30% and 5 h)11.5606.5[16] Bacillus licheniformis ATCC9945a (BliAmy)NM58% (30% and 5 h)11.5606.5[16] Bacillus licheniformis (BLA, Sigma)35% (30% and 4 h)43% (30% and 4 h)1.0307.0This study Pontibacillus sp. ZY (AmyZ1)37% (30% and 4 h)47% (30% and 4 h)5.0 b or 1.0 c 307.0This studyFungi and other Rhizomucor sp.…”

“…α-Amylases from B. licheniformis are considered as thermostable enzymes and widely used in starch liquefaction process [6]. Some literatures also reported that the α-Amylases from this genus possessed potency of raw starch digesting [6, 16]. However, when compared with commercial α-amylase BLA, AmyZ1 exhibited higher efficiency towards 30% raw corn starch, with less amount of AmyZ1 required.…”

“…Typically, starch-processing industries employ 20–30% (w/v) starch slurries [16]. Systematic studies with the enzymes from Bacillus licheniformis [16, 17], B. amyloliquefaciens [12], Bacillus subtilis [4, 17], and G. thermoleovorans [12, 18] have demonstrated that improved hydrolysis toward high concentration raw starches can be achieved by increasing the incubation temperature to 60 °C or higher [19]. An alternative strategy to obtain better hydrolysis is to extend the reaction time at lower temperatures [16].…”

“…Systematic studies with the enzymes from Bacillus licheniformis [16, 17], B. amyloliquefaciens [12], Bacillus subtilis [4, 17], and G. thermoleovorans [12, 18] have demonstrated that improved hydrolysis toward high concentration raw starches can be achieved by increasing the incubation temperature to 60 °C or higher [19]. An alternative strategy to obtain better hydrolysis is to extend the reaction time at lower temperatures [16]. However, neither increasing temperature nor extending incubation time helps to reduce energy consumption and lower the cost of manufacturing.…”