Primary Study on the Amylase and Cellulase Fermented in Aspergillus Oryzae
|School||Tianjin University of Science and Technology|
|Course||Nutrition and Food Hygiene|
|Keywords||Soy sauce Aspergillus oryzae Amylase Cellulase|
Aspergillus oryzae is the main fungi for soy sauce brewing, the enzyme production activity of which is crucial to the making of soy sauce koji and soy sauce fermentation. Aspergillus oryzae3.042is a traditional strain with advantageous characteristics such as high enzyme activity and spores producing ability and is still widely used in soy sauce fermentation. However, the defects such as relatively low acid protease handicap the use in the low pH environment during the later phase of soy sauce brewing. Thus, the raw materials utilization rate is low, and would impact of soy sauce flavor and quality.Aspergillus oryzae A100-8was a new mutant strain induced by nitrogen ion implantation technology and screened on the casein medium based on the traditional soy sauce brewing strain A. oryzae3.042. It was proved by the previous laboratory experiments that the protease activity of A. oryzae A100-8was relatively higher than that of A. oryzae3.042.This study primarily analyzes the difference between the mutant strains and the traditional strains from the aspect of amylase and cellulose. Primarily, by culturing the strains in the small chamber, observing their mycelium morphology via fluorescence microscopy. Compared to A. oryzae3.042, relatively sturdier cell wall and much higher density diaphragm of A. oryzae A100-8was observed. Secondly, the activities of the amylase and cellulose of the two strains were compared by a transparent circle observation. A. oryzae A100-8showed larger amylase and cellulose activity than A. oryzae3.042. Then the relationship between enzyme activity and factors which affected the activity of the amylase and cellulose were determined respectively. Further by primers design of the major genes related to the amylase and cellulose, and by semi-quantitative RT-PCR method to the relative expression levels of genes were explored. Relative expression levels of genes involving with amylase and cellulose of the two strains showed the relative expression levels of mylase and cellulose of A. oryzae A100-8were higher than those of A. oryzae3.042. Then the HS-SPME and GC-MS were used to analyze the volatile flavors in the soy sauce koji and soy sauce fermented by the two strains. Lastly the variety and content of the amino acids were detected by amino acid analyzer on soy sauce koji. Study on the koji volatile flavors proved that A. oryzae A100-8generated more ketones, aldehydes, alcohols, esters, furan compounds and amino acids, especially sweet and umami flavor amino acids making the flavor of koji and soy sauce more comfortable and pleasant.