Activities And Applications Of Various Glycosidases In Water Kefir

Water kefir grains are a naturally occurring complex strain in which certain microorganisms produce extracellular polysaccharides,which enclose various types of microorganisms together to form irregular transparent colloidal particles.It is composed of lactic acid bacteria,acetic acid bacteria,and yeast.Traditionally,it is used to ferment brown sugar water or juice to make beverages.The results of pre-macrogenome sequencing showed that there are abundant glycosidase genes in water kefir grains,and it is presumed that they have strong ability to hydrolyze glycosides.However,there is a related research on glycosidases in water-free Kefir grains at home and abroad.Most of the active ingredients are often linked with glycosyl groups in the form of glycosides,often do not have biological activity or activity is low,the specific biological activity required to be converted to aglycone by specific glycosidase is significantly improved.Soybean isoflavone aglycone has higher biological activity than soy isoflavone glucoside.In this dissertation,we used water kefir to ferment isoflavone glucosides to increase isoflavone glucoside content.Simultaneously,the correlation between?-glucosidase activity and aglycone production was studied.The banana peel contained a lot of flavonoids in the form of glycosides.Physical substances,and pectin,polyphenols and other available components are abundant.In this paper,water kefir grains were used to ferment banana peels,releasing polyphenols and volatile components,and degrading polysaccharide molecules such as pectin to obtain rich fermented fruits and vegetables.Aroma broth.The main findings of this paper are as follows:(1)The enzymatic activities of various glycosidases in water kefir grains and water kefir grains were analyzed.In 48 h brown sugar water fermentation broth,the activity of pectinase in water kefir grains and fermentation broth was 210 U/g and 322 U/mL;xylanidase activity was 2.67±0.05 U/g and 1.68±0.05 U/mL,respectively;?-glucosidase activity was 0.22±0.01 U/g and 0.12±0.01 U,respectively.The cellulase activity was 0.01±0.02 U/g and 0.03±0.01 U/mL,respectively.The activity of pectinase was higher in water kefir grains and fermentation broth;the activities of xylosidase and?-glucosidase were water kefir grains>fermentation broth,and the cellulase activity was compared in both parts.low.In the 62 h soy flour fermentation broth,the?-glucosidase activity in the pellets and supernatants obtained by centrifugation of the water kefir pellets and the fermentation broth was 0.07±0.01 U/g,57.9±0.1 U/mL respectively.At 0.01 U/mL,the?-glucosidase activity in the precipitate obtained by centrifugation was significantly increased,indicating that the glycoside compounds in the soybean meal can induce the production of?-glucosidase by the microorganisms in the fermentation broth,and the enzyme is an intracellular enzyme.(2)The fermentation process conditions of the water kefir grain-fermented soybean meal and the conversion of isoflavone glucosides to aglycones were studied.The results showed that the fermentation time,fermentation temperature and the amount of soybean meal had a significant effect on the yield of soybean isoflavone aglycone,and the response was adopted.The optimum process conditions were optimized by the surface method as follows:based on the volume of distilled water in the fermentation as 100%,5.5%soybean powder was added,the inoculum amount was5%,the fermentation time was 62 hours,no brown sugar was added,and the fermentation temperature was 30°C.The total isoflavone glucosides were converted into aglycone,and the total amount of isoflavone aglycone in soybean meal reached1320?g/g after fermentation.At the same time,it was found that?-glucosidase activity and soybean isoflavone aglycone content were found in the fermentation broth.(3)The technological conditions of water kefir pellets for fermenting banana peels were studied.Through single-factor tests(fermentation time,amount of added banana peels,and amount of brown sugar),the sensory evaluation of the optimum fermentation conditions was as follows:the volume of distilled water in the fermentation was 100%.The amount of brown sugar added was 10%,the amount of banana peel was 30%,the inoculation amount was 5%,and the fermentation time was6 days.The number of Lactobacillus in the fermentation broth of banana skin increased with the prolongation of fermentation time from 0 to 6 days,and the highest value was 8.50±0.20 lgcfu/mL,which was 103 times higher than the number of live bacteria in probiotics drink standard;The content of polyphenols was 58.42±1.20?g/mL.After fermentation,the total phenolic content was up to 105.1±1.5?g/mL,and the total phenolic content after fermentation was increased by 79.88%.The contents of lactic acid and acetic acid were 5.94 mg/mL and 10.54 mg/mL,respectively.The mL and soluble solids content of 4.0%showed a good negative correlation.The banana skin was fermented with water kefir to produce isoamyl butyrate,isoamyl isovalerate and other lipid compounds,which gave good fermentation broth.The taste of fermented fruits and vegetables.(4)The volatile components of banana peel were significantly changed before and after fermentation.The total ion peak area of unfermented banana peel was 3.2×10~6,and the total ion peak area of the fermentation broth after 6 days of fermentation with water kefir reached 7.5×10~6.Compared with unfermented banana peel,it was increased by 2.3 times,and 47 kinds of volatile components were detected in unfermented banana peel,accounting for 79.89%of the total,mainly esters,22 in total,accounting for 60.08%,the 6th day of bananas.A total of 64 volatile components were detected in the fermentation broth,which accounted for 88.35%,compared with 8.46%in unfermented banana peels,and 33 in esters in the fermentation broth,accounting for 64.62%,including bananas.The characteristic aroma substance isopentyl isovalerate,which accounts for 2.95%of the unfermented banana peel,and in the 6th day of the banana peel fermentation broth,the proportion of 7.19%,an increase of 2.4 times;isoamyl butyrate,which In the unfermented banana peels,the ratio was 21.62%.In the Kefir grains,the proportion of the fermented liquid of the banana peel was 21.79%,and other esters also increased.