Fang Wei, Xue Saisai, Deng Pengjun, Zhang Xuecheng, Wang Xiaotang, Xiao Yazhong, Fang Zemin
1School of Life Sciences, Anhui University, Hefei, 230601 Anhui China.
Anhui Key Laboratory of Modern Biomanufacturing, Hefei, 230601 Anhui China.
Biotechnol Biofuels. 2019 Apr 23;12:95. doi: 10.1186/s13068-019-1432-9. eCollection 2019.
Starch is an inexpensive and renewable raw material for numerous industrial applications. However, most starch-based products are not cost-efficient due to high-energy input needed in traditional enzymatic starch conversion processes. Therefore, α-amylase with high efficiency to directly hydrolyze high concentration raw starches at a relatively lower temperature will have a profound impact on the efficient application of starch.
A novel raw starch digesting α-amylase (named AmyZ1) was screened and cloned from a deep-sea bacterium sp. ZY. Phylogenetic analysis showed that AmyZ1 was a member of subfamily 5 of glycoside hydrolase family 13. When expressed in , the recombinant AmyZ1 showed high activity at pH 6.0-7.5 and 25-50 °C. Its optimal pH and temperature were 7.0 and 35 °C, respectively. Similar to most α-amylases, AmyZ1 activity was enhanced (2.4-fold) by 1.0 mM Ca. Its half-life time at 35 °C was also extended from about 10 min to 100 min. In comparison, AmyZ1 showed a broad substrate specificity toward raw starches, including those derived from rice, corn, and wheat. The specific activity of AmyZ1 towards raw rice starch was 12,621 ± 196 U/mg, much higher than other reported raw starch hydrolases. When used in raw starch hydrolyzing process, AmyZ1 hydrolyzed 52%, 47% and 38% of 30% (w/v) rice, corn, and wheat starch after 4 h incubation. It can also hydrolyze marine raw starch derived from , resulting in 50.9 mg/g DW (dry weight of the biomass) of reducing sugars after 4 h incubation at 35 °C. Furthermore, when hydrolyzing raw corn starch using the combination of AmyZ1 and commercial glucoamylase, the hydrolysis rate reached 75% after 4.5 h reaction, notably higher than that obtained in existing starch-processing industries.
As a novel raw starch-digesting α-amylase with high specific activity, AmyZ1 efficiently hydrolyzed raw starches derived from both terrestrial and marine environments at near ambient temperature, suggesting its application potential in starch-based industrial processes.
淀粉是一种用于众多工业应用的廉价且可再生的原材料。然而，由于传统酶法淀粉转化过程需要高能量输入，大多数淀粉基产品成本效益不高。因此，能够在相对较低温度下高效直接水解高浓度生淀粉的α-淀粉酶将对淀粉的高效应用产生深远影响。
从深海细菌ZY中筛选并克隆出一种新型生淀粉消化α-淀粉酶（命名为AmyZ1）。系统发育分析表明，AmyZ1是糖苷水解酶家族13第5亚家族的成员。当在大肠杆菌中表达时，重组AmyZ1在pH 6.0 - 7.5和25 - 50℃下表现出高活性。其最适pH和温度分别为7.0和35℃。与大多数α-淀粉酶类似，1.0 mM Ca可使AmyZ1的活性增强（2.4倍）。其在35℃下的半衰期也从约10分钟延长至100分钟。相比之下，AmyZ1对生淀粉具有广泛的底物特异性，包括来自大米、玉米和小麦的淀粉。AmyZ1对生大米淀粉的比活性为12,621±196 U/mg，远高于其他报道的生淀粉水解酶。在生淀粉水解过程中，孵育4小时后，AmyZ1可水解30%（w/v）大米、玉米和小麦淀粉的52%、47%和38%。它还能水解来自的海洋生淀粉，在35℃孵育4小时后产生50.9 mg/g DW（生物质干重）的还原糖。此外，当使用AmyZ1和商业糖化酶组合水解生玉米淀粉时，反应4.5小时后水解率达到75%，明显高于现有淀粉加工行业的水解率。
作为一种具有高比活性的新型生淀粉消化α-淀粉酶，AmyZ1在接近环境温度下能高效水解来自陆地和海洋环境的生淀粉，表明其在淀粉基工业过程中的应用潜力。
