抗菌肽Adenoregulin基因工程菌培养条件的优化及分批发酵研究

denoregulin（ADR）是来源于南美树蛙Phyllomedusa bicolor皮肤的含有33个氨基酸的抗菌肽,在非极性环境中形成α_螺旋型结构,具有抗菌活性强、抗菌谱广的特点。将ADR基因克隆于pET32a载体上,转化大肠杆菌BL21(DE3),对这一工程菌株的培养条件进行了优化。通过正交试验,考察诱导时机、诱导剂量和诱导时间三个因素的不同水平对蛋白表达的影响,结果发现诱导时机的影响尤为显著,考察了9种不同培养基对表达量的影响,发现培养基中加入葡萄糖对目标蛋白的稳定表达起了重要的作用,确定最佳培养条件为：培养基为2×YT+0.5%葡萄糖,诱导时机为OD600=0.9左右,诱导剂IPTG加入的终浓度为0.1mmol/L,诱导时间为4h。采用前期恒pH、后期指数流加的策略进行工程菌BL21(DE3)/pET32a-adr的高密度培养,在整个流加过程中,通过控制葡萄糖的加入量,将菌株的比生长速率控制在015h^-1,乙酸浓度也被控制在较低的水平(<2g/L),但是质粒丢失严重,在发酵结束时,约有40%的大肠杆菌中不带质粒,这导致了目标蛋白的表达量下降严重,但是表达的目标蛋白90%以上为可溶性形式。表达的融合蛋白无抑菌活性,而裂解后得到的ADR单体具有明显的抑菌活性。     

Production and purification of a novel antibiotic peptide,adenoregulin, from a recombinant <Emphasis Type="Italic">Escherichia coli</Emphasis>

Adenoregulin is a member of dermaseptin family which are vertebrate antibiotic peptides having lethal effects against a broad spectrum of bacteria, fungi and protozoa. The 99 bp adenoregulin gene was cloned in the expression vector pET32a and transformed into Escherichia coli BL21(DE3). In fed-batch cultivation of BL21(DE3)/pET32a-adr, an exponential feeding strategy was applied to gain 60 g dry cells l^–1. The recombinant fusion protein Trx-ADR was expressed in a soluble form. The fusion protein was isolated by Ni²⁺-chelating chromatography, cleaved with CNBr and purified to homogeneity through reverse phase-HPLC and size exclusion-HPLC. The purified recombinant adenoregulin had antibacterial activity against Escherichia coli K12D31 with apparent Mr of 3.4 kDa, identical to the anticipated value.     

Display of adenoregulin with a novel <Emphasis Type="Italic">Pichia pastoris</Emphasis> cell surface display system

Two Pichia pastoris cell surface display vectors were constructed. The vectors consisted of the flocculation functional domain of Flo 1p with its own secretion signal sequence or the α-factor secretion signal sequence, a polyhistidine (6×His) tag for detection, an enterokinase recognition site, and the insertion sites for target proteins. Adenoregulin (ADR) is a 33-amino-acid antimicrobial peptide isolated from Phyllomedusa bicolor skin. The ADR was expressed and displayed on the Pichia pastoris KM71 cell surface with the system reported. The displayed recombinant ADR fusion protein was detected by fluorescence microscopy and confocal laser scanning microscopy (CLSM). The antimicrobial activity of the recombinant adenoregulin was detected after proteolytic cleavage of the fusion protein on cell surface. The validity of the Pichia pastoris cell surface display vectors was proved by the displayed ADR.