Study On The Diversity And Characteristics Of The Culturable Microorganisms From Traditional Fermented Vegetable Food-jiangshui In Northwest Of China

Jiangshui is a traditional fermented vegetable food in the Northwest of China, especiallyin summer in Gansu, Ningxia and Shannxi Province. Jiangshui is pretty popular for itsfragment and delicious acting as a side dish in lunch-meal. On the other hand, Jiangshui is akind of favorite drinking in summer for cooling and quenching thirsty. However, theJiangshui processing way is followed by traditional style just as natural fermentation. Everyfamily can do it in kitchen, therefore the quality is not always good as expected. As aimportant local food, there is not so many studies on the quality controlling as well asdominant strains in fermentation processing. So, it is necessary to declare some key factors inJiangshui fermentation. The screening and identifying the functional dominant strains is themain purpose of this thesis. Meanwhile, some special strains with super function on degradingcholesterol and nitric reduction were researched. In the study,5samples of Jiangshui werecollected from Shapotou Ningxia, Gannan, Qingyang, Tianshui and Lanzhou in Gansu, fivedifferent regions in the Northwest of China. We use different mediums to culture differentstrains from the materials. After identifying these strains by biochemical characters as well as16SrDNA and18SrDNA technologies,107strains were screened. Some highlighted resultswere listed as followed:（1）107strains were isolated and purified from the samples of Jiangshui in the fivedifferent regions in the Northwest of China, identified into89kinds of bacteria,19kinds ofmold and1kind of yeast.（2）Through the diversityanalysis found that the total strains belonged to21genus.Themajority of strains were belonged to lactobacillus. They occupied the33.65%of the totalstrains. The second group were classified the Lactococcus and penicillium. The rates were10.28%and14.02%, respectively. The left strains were belonged to streptococcus andLeuconostoc, they were relative small groups though. There existed similarities anddifferences in culturable microbial components of Jiangshui samples in various areas ifcontrastive analysis was conducted on all the samples. The same bacteria dominatedfermentation, which were the main similarities. However, harmful bacteria were different inthe different samples of Jiangshui.（3）The purified strains were studied through the characteristic of producing acid,reducing cholesterol and nitrite to which most of the bacterial strains contained in Jiangshuihad a good ability. However, different strains had different ability to produce acid, reducecholesterol and nitrite. （4）7strains were screened from these materials based on the super abilities ofdegrading cholesterol. These strains were identified Lactococcus lactis subsp. cremoris (Q2),Lactococcus lactis subsp. lactis (M2and H1), Brevibacterium casei (M5and H4),Lactobacillus fermentium (M14), Lactococcus Raffinolactis (Q7).（5）Moreover, The research showed that7strains had different characters in Jiangshuifermentation.①Q2(L. lactis subsp. cremoris) and H1(L. lactis subsp. lactis) had thestrongest salt-tolerant ability.②Q2(L. lactis subsp. cremoris), Q7(L. Raffinolactis), H1(L.lactis subsp. lactis) and M14(L. fermentium) had good acid resistance, meanwhile Q2(L. lactissubsp. cremoris) strain was the best one in the7strains.③Q2(L. lactis subsp. cremoris)、M2(L. lactis subsp. lactis)、M14(L. fermentium)、Q7(L. Raffinolactis) shared good ability forbile salt resistance.④All the7strains had certain ability of anti-bacterial properties. In them,the M14(L. fermentium) and the M2(L. lactis subsp. lactis) were better than others.