Separation & Identification Of Mould And Optimization Of Culture Conditions From The Traditional Sauce Koji

The traditional flour paste and soybean paste are two kinds of seasoner with special flavour, which were fermented by microorganisms of using natural inoculation, such as Aspergillus oryzae and Aspergillus niger. This article took the traditional sauce koji as studying object. Firstly, the activity for enzyme production of strains separated and identified with spread-plate and streaking method from traditional sauce koji was compared. And then eight strains of mould were selected to further identify by PCR. Secondly, the culture conditions of mould producing the highest activity of neutral protease were optimized by single factor and response surface methodology. Thirdly, the dynamic changes of the activity for enzyme production of strains and physicochemical parameters were studied during fermentation processing of the sweet flour paste coupled multi-strains. These studies will provide theoretical basis for multi-strains starter of the sweet flour paste. The conclusions are as followed:1,14 mould strains (including 7 Aspergillus oryzae ,6 Aspergillus nigerand and Rhizopus oryzae) were separated and identified by observing morphological characteristics. And then eight strains of mould including 2 Aspergillus niger which had more ability of acid protease and diastase production , 5 Aspergillus oryzae and Rhizopus oryzae which had more ability of neutral protease and diastase production were selected to further identify by PCR amplification technique with 26SrDNA sequence analysis. 5 Aspergillus oryzae and 2 Aspergillus niger were identified with the similarity of the highest homology (100%)of strains .2,The optimum culture conditions of Aspergillus oryzae selected were time 54h,humidity 90%,temperature 31℃,and its enzyme productivity was 1766.63U/g.3,The dynamic changes of the main enzyme productivity and main physical and chemical indexes of the mould during the fermentation .The pH of sauce mash fell sharply during 0~10 days of fermentation, fell slowly after 10 days, and steadied at 4.4~4.5 after 50 days. Total acidity of sauce mash rose sharply during 0~10 days of fermentation, rose slowly after 10 days, steadied at 4.6%~4.8% after 50 days. The activity of neutral protease decreased by half at 20 days, closed to zero after 50 days of fermentation. The content of amino-nitrogen went up faster during 0~30 days of fermentation, slowly after 30 days, steadied at 0.38g/100g after 50 days. The activity of diastase declined sharply during 0~42 days of fermentation, then steadied at 400 U/g at last. The content of reducing sugar attained 18.2g/100g at 32 days, rose slowly after 32 days, steadied at 21.3g/100g after 43 days.