Study On Separation,Identification And Performances Of Acid-producing Microorganis From Hengshui Laobaigan Liquor

Organic acids are important wine taste compounds and precursors of flavor components.Organic acids in liquors generate mainly from the microbial metabolism,so it is necessary to study their acid-producing bacteria for improving and controling organic acids in liquors.So far,some investigations on isolation,identification,acid-producing performances and application of acid-producing bacteria in liquors have been done,however,few reports deal with the acid-producing microorganisms for Laobaigan flavor.Six kinds of organic acids,i.e.lactic acid,propionic acid,isobutyric acid,butyric acid,isovaleric acid and acetic acid,were detected from Hengshui Laobaigan liquors by gas chromatography and high performance liquid chromatography(HPLC),e.g.,the contents of lactic acid,acetic acid and propionic acid were 110.34 mg/100 mL,38.03 mg/100 mL and 1.64 mg/100 mL,respectively.The testing results showed that 69 strains of acid-producing bacteria were separated from okuma and fermented grains.Seven strains with different forms were chosen via the study on colonial morphology,physiological and biochemical characteristics.The products from above-mentioned seven strains were measured,and the results revealed that the producing amounts of lactic acid from bacterium No.26,acetic acid from bacterium No.1,and propionic acid from bacterium No.5 were the largest,respectively.The 16 S rDNA molecule of bacteria No.1,5 and 26 were identified,and the results showed that the bacteria No.1,5 and 26 were Pap acetic acid bacteria(Acetobacter pasteurianus),Cereus bacteria Bacillus(Bacillus cereus)and lactic acid bacteria(Weissella cibaria),respectively.The culture conditions and media of acid-producing bacteria were optimized via the single factor experiment and orthogonal test,and the optimum conditions and media compositions for acid-producing bacteria were obtained.Based on the optimization of liquid culture conditions,the pure acid-producing bacteria were added in fermented grains to simulate solid-state fermentation of liquor.After distillation of the fermented grains containing some acid-producing bacteria,the amounts of lactic acid,acetic acid and propionic acid in liquors were obviously higher than those in the fermented grains without acid-producing bacteria;and the acid-producing amounts were the highest when the amount of fermented grains was 10~5/g.The enhanced temperature was advantageous to the production of organic acids in the investigated temperature range.With increasing the fermentation number of fermented grains,the amount of acetic acid increased while the amounts of lactic acid and propionic acid decreased.