Preparation Of Immobilized Acetic Acid Bacteria Using Adsorption-Embedding Immobilization Method And Its Application In Malt Vinegar

Immobilized cells technology with a faster rate but a shorter fermentation period for stablequality, which can be easily applicated in continuous production. However, the selection of carriersis vital in immobilized fermentation. But the traditional choice of the carrier more consider thecharacteristics of material itself, while ignoring the effect of carrier materials on microbial cellsbiological characteristics and practical operability, thereby limiting the application of immobilizedcells in some fields, especially for aerobic bacteria such as acetic acid bacteria.Generally, immobilized cell carriers are divided into three categories: natural, synthetic andcomposite ones. Natural carrier is often non-toxic and have a good mass transfer performance, buta low intensity, such as alginate and corncob; synthetic carrier has a hard intensity and goodstability, but poor mass transfer performance and a poor cell activity, such as polyvinyl alcohol;composite carrier owns comprehensive application prospect due to both advantages above.In this paper, the immobilization of acetic acid bacteria, the main strain of the malt vinegarbrewing, taking corncob, sodium alginate, polyvinyl alcohol, corncob-SA and corncob-PVA ascarrier was studied. In order to provide a theoretical basis for malt vinegar production byimmobilized technology, the immobilized conditions and the technical parameter for malt vinegarbrewing by immobilized technology were optimized. In addition, we also designed an immobilizedcell reactor and compared the malt vinegar brewing by free and immobilized cell. The mainresearch conclusions in this study showed as follow:1. The use of corncob, sodium alginate, polyvinyl alcohol, corncob-SA and corncob-PVA ascarrier for acetic acid bacteria immobilization was studied. The results showed that corncob-PVAwas an efficient and quality acetic acid bacteria immobilized carrier. The optimum parametersthrough single factor test and Box-Behnken central composite experimental design were as follows:bacterial suspension concentration was0.7g/100mL, adsorption time was12h, PVA concentration was13%, the ratio of PVA and corncob was2:1, freezing temperature was-20℃, the cycles offreezing-thawing was3.2. The best optimal technical parameters through single factor test and Box-Behnken centralcomposite experimental design were as follows: inoculums amount was10.11%(m/v), initialalcohol degree was6.26%(v/v) and fermentation temperature was32℃, rotate speed was171r/min in acetic acid fermentation stages used immobilized acetic acid bacteria.3. Brewing malt vinegar by immobilized acetic acid bacteria, fermentation period was only96hours, acidity was4.73g/100mL and acidity yield rate was0.48g/L·h; and the stability ofimmobilized particles was fine, fermentation performance of immobilized particles was notsignificant decline for continuous use six times.4. Comparing the malt vinegar between free and immobilized acetic acid bacteria brewed.The results showed that acidity yield rate was increased by37%, fermentation period wasshortened by25%in acetic fermentation stages compared to free ones; meanwhile, the sensorycharacteristics, physicochemical and hygienic properties of malt vinegar brewed by immobilizedtechnology was no significant difference compared to free ones.