无IPTG添加，在T7启动子下大肠杆菌高效异源表达纤维二糖差向异构酶

In view of the phenomenon that cellobiose 2-epimerase from Caldicellulosiruptor saccharolyticus (CsCE) can be expressed efficiently and the expression level is better than that the addition of isopropyl-beta-D-thiogalactopyranoside (IPTG) in TB media. M9 media was used to study the effects on the expression level of natural organic substances yeast extract and peptone. The results showed that the enzyme activity of cellobiose 2-epimerase in TB media reached 6.13 U/mEfficiently heterologously expressing cellobiose 2-epimerase gene in Escherichia coli (E. coli)under promoter T7 without addition of IPTGL without addition of IPTG, it was 5.02-fold higher than the activity observed when 1.0 mM IPTG was added. In the absence of IPTG, cellobiose 2-epimerase gene in E. coliBL21 pET28a-CsCE could not be expressed in M9 media. But it was expressed in M9 media without addition of IPTG when tryptone T-O or yeast extract Y-O were added, respectively. It was verified that both yeast extract Y-O and tryptone T-O contain inducers that can induce the transcriptional expression of the cellobiose 2-epimerase gene in E. coli BL21 pET28a-CsCE. In the absence of IPTG, the addition of soy peptone T-A1 or yeast extract Y-A1 significantly upregulated the expression of cellobiose 2-epimerase gene in E. coli BL21 pET28a-CsCE, and these inductions led to higher expression levels compared to tryptone T-O or yeast extract Y-O. In the media TB-A1 containing yeast extract Y-A1 and soy peptone T-A1, the activity of cellobiose 2-epimerase reached 6.88 U/mL, representing a 2.02-fold increase compared to previously reported maximum activity in E. coli without addition of IPTG. This study can provide an important reference for realizing recombinant enzyme expression in E. coli without addition of IPTG.