Vc二步发酵离体实验系统的建立

以氧化葡萄糖酸杆菌和巨大芽孢杆菌混合培养物的无细胞抽提液为基本反应液，在试管中建立了Vc二步发酵离体实验系统，将底物山梨糖加入反应体系后在pH7．0，35℃下保温24h，2－酮基－L－古龙酸生成，加入巨大芽孢杆菌胞外活性物质对离体系统的产酸没有影响，一定量的L－山梨糖脱氢酶可促进产酸，试验了pH、θ／℃、金属离子、电子受体、去污剂等对该系统产酸的影响，并就其作用机理进行了探讨，结果表明离体系统产酸的最适pH和θ／℃分别是8和．40℃，Fe^3 促进产酸，Co^2 抑制产酸2，6－二氯酚定酚作为电子受体促进细胞膜组分产酸，但对细胞质组分没有影响，Triton X-100和Tween80抑制产酸。

THE ESTABLISHMENT OF AN IN VITRO EXPERIMENT SYSTEM FOR VITAMIN C TWO-STEP FERMENTATION

An in vitro experiment system for vitamin C(Vc) two-step fermentation has been developed using the cell-free extract of Gluconobacter oxydans and Bacillus megaterium as the basal reaction solution. 2KGA could be detected with the standard method in the experiment system containing 200 mmol/L L-sorbose, at pH 7.0 and 35℃ after 24 h. The bioactive metabolites from the culture supernatant of Bacillus megaterium which enhanced efficiently the production of 2KGA in G.oxydans fermentation didn’t have any effects on the production of 2KGA in the in vitro system. Purified L-sorbose dehydrogenase from G.oxydans promoted the 2KGA productivity in the in vitro system. The effects of pH，temperature，metals，electron accepter and detergents on 2KGA productivity and their affecting mechanism in the in vitro system were studied. The results showed that optimum pH andθ/℃ were 8 and 40℃,2,6-Dichlorophenol indophenol and Fe3+ stimulating 2KGA production, Co2+,Triton X-100 and Tween 80 inhibiting 2KGA production. Fig 8, Ref 7