Study On Weakening The Dependency Of Acid-producing Strain On The Companion Strain In Vc Fermentation

Vitamin C production with two-step fermentation technology was invented by Chinese scientist Yin Guanglin. Acid-producing strain commonly known as small bacterium grows slowly with low acid production, and companion strain commonly known as large bacterium promotes the growth and acid production of small bacterium. Therefore the fermentation for producing 2-keto-gulonic acid (2-KLG) always depends on companion bacterium and it is difficult to control in the Vc industrial production. The purpose of this study is to weaken the dependency of acid-producing strain on the companion strain in Vc fermentation without reducing the yield of acid production.The method is using extracellular supernatant of companion strain and acid-producing strain to replace the existing seed, and also by adding the companion strain into new mixed fermentation to weaken the dependency of the acid-producing strain on the companion strain. The results of the study are as follows:1.The companion strain grows faster in the 0.5% glucose medium without sorbose than in the ordinary culture medium. And the spores burst after 22 h.2. The extracellular supernatant was used to replace the companion strain and the acid production capacity of new mixed fermentation was better than traditional mixed cultures. It proved that extracellular supernatant could replace the companion bacterium. By adding the extracellular supernatant into small bacterium and the supplement of companion bacterium at 10 h. the yield of 2-KLG increased 9.1%.3. Adding the extracellular supernatant into companion strain of 25b-1 increased 2-KLG production 11.8% and the supplement of companion strain of 25b-1 at 24 h increased 2-KLG production 17%.4. Adding 1/3 of extracellular supernatant into wort improved the efficiency of Vc two-step fermentation and the acid production capacity increased by 24.3% than control. The optimum adding time of supplement of companion strain of 25b-1 was at 8h which promoted 2-KLG production in the new mixed fermentation.5. The proteins with molecular weight of 60KDa-80KDa in extracelluar supernatant was discovered through SDS-PAGE except the previous reported mainly proteins with molecular weight of 3OKDa-5OKDa and 35KDa-100KDa.6.2-KLG production capacity increased by 6.9%,11% and 13.7% respectively corresponding to the addition of 1%,2%,5% protein residues into fermentation medium respectively. So protein residues could promote the production of 2-KLG in the vitamin C two-step fermentation in order to weaken the dependency of acid-producing strain on the companion strain. It is significant to the vitamin C industrial production by reusing the resources.