本试验旨在对重组菌丝霉素发酵培养基进行优化筛选,并研究饲粮中添加重组菌丝霉素对断奶仔猪生长性能、养分消化率和肠道微生物菌群的影响。试验利用30 L发酵罐对毕赤酵母基因工程菌(PPle)进行液体发酵,采用分批-补料式发酵工艺,比较低盐、基础甘油和基础可溶性淀粉3种不同培养基对重组菌丝霉素分泌表达的影响。动物试验选用30头24日龄健康的"杜长大"断奶仔猪,按体重一致原则随机分配到5个组:对照组(CON组,基础饲粮)、硫酸黏菌素组(CS组,基础饲粮＋0.3%硫酸黏杆菌素)、抗菌肽组(AP组,基础饲粮＋0.2%重组菌丝霉素)、微生态制剂组(PB组,基础饲粮＋0.1%微生态制剂)和联合应用组(PPB组,基础饲粮＋0.2%重组菌丝霉素+0.1%微生态制剂),试验期21 d。结果表明:发酵到114 h,低盐组、基础甘油组和基础可溶性淀粉组菌体湿重达到最高,分别为450、402、277 g/L。发酵114 h,测得发酵上清液蛋白总浓度低盐组0.38 g/L、基础甘油组3.94 g/L、基础可溶性淀粉组5.63 g/L。动物试验表明,与CON组相比,CS组和AP组显著提高了平均日采食量(ADFI)和平均日增重(ADG),显著降低了料重比(F/G)(P<0.05)。与CON组相比,CS组和AP组有降低腹泻率的趋势(0.05<P<0.10)。与其余各组相比,AP组显著提高了回肠食糜双歧杆菌的含量(P<0.05)。与CON组相比,其余4个组有提高能量和干物质表观消化率的趋势(0.05<P<0.10)。PB组磷的表观消化率极显著高于其余4个组(P<0.01)。综上所述,通过优化培养基,提高了重组菌丝霉素的表达量,在断奶仔猪饲粮中添加重组菌丝霉素可改善仔猪的生长性能。
The study was aimed to investigate the optimization and screening of fermentation medium for the recombinant plectasin, and the effects of recombinant plectasin on growth performance, nutrient digestibility and intestinal microflora in weaning pigs. In the present study, the liquid fermentation was used to prepare the recombinant plectasin in a 30 L fermenter by using batch-fermentation process, and subsequently the expression levels of recombinant plectasin with low salt, basal glycerin and basal soluble starch mediums were compared. Thirty healthy piglets (Duroc× Landrace×Yorkshire) weaned at 24 d were selected and randomly allotted to five groups according to their initial BW. The groups consisted of control group (CON group, a basal diet without antibiotic), sulfuric acid colistin group (CS group, basal diet+0.3% sulfuric acid colistin), antimicrobial peptide group (AP group, basal diet+0.2% recombinant plectasin), probiotics group (PB group, basal diet+0.1% probiotics) and joint application group (PPB group, basal diet+0.2% recombinant plectasin+0.1% probiotics). The experiment lasted for 21 days. The results showed that the wet weight of bacteria in low salt group, basal glycerol group and basal soluble starch group reached the highest value at 114 hours of fermentation, which were 450, 402 and 277 g/L, respectively; the concentrations of total protein in supernatant were 0.38, 3.94 and 5.63 g/L, respectively. Animal trial results showed that compared with CON group, average daily feed intake (ADFI), average daily gain (ADG) and ratio of feed to gain (F/G) were significantly increased (P<0.05) and diarrhea incidence tended to decrease in CS and AP groups (0.05<P<0.10). Compared with other groups, the AP group significantly increased the population of Bifidobacteria in ileal digesta (P<0.05). Compared with CON group, the other groups tended to increase the apparent digestibility of energy and dry matter (0.05<P<0.10). The apparent digestibility of phosphorus in PB group was significantly greater than that in the rest four groups (P<0.01). In conclusion, the yield of recombinant plectasin and the performance of piglets are improved by optimizing the growth medium. And the results preliminarily confirm that recombinant plectasin developed by our laboratory can be used as an alternative to antibiotics in animal feed.
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