土壤中单宁和植酸降解菌的筛选、鉴定及液态发酵研究

annic acid and phytic acid are two important anti-nutritional factors that limit the utilization of plant ingredients for aqua-feed industry. Enrichment-culture technique was used to isolate, screen and identify efficient microorganisms from soil that degraded both tannic acid and phytic acid. In this study, 109 microorganisms were isolated, of which 27 isolates exhibited phytic acid degradation potential and 14 isolates exhibited tannic acid degradation potential. Among these isolates, fungi M-6, M-3 and M-1 possessed the capacity of degradation in both tannic acid and phytic acid, of which fungus M-6 had higher degradative capacity than fungi M-3 and M-1. With the increase of fermentative temperature (20℃-35℃), the activities of tannase and phylase of fungus M-6 all showed a firstly increase and then decrease trend, with the highest activities observed at 30℃ (P<0.05). With the increase of fermentative pH (4-7), the activities of tannase and phylase of fungus M-6 all firstly increased and then decreased (P<0.05). The activity of tannase of pH 5 treatment was significant higher than other groups (P<0.05), the activity of phylase of pH 5 group was significantly higher than pH 4 and 7 groups (P<0.05) whereas showed no difference with pH 6 treatment (P>0.05). The isolate fungus M-6 was characterized as Aspergillus niger, supported by the morphologic taxonomy as well as the similarity of the sequences of the ITS1-5.8S-ITS2 ribosomal DNA region. Therefore, fungus M-6, M-3 and M-1 possessed the capacity of degradation in both tannic acid and phytic acid, the optimum fermentative temperature of fungus M-6 was 30℃ and the optimum fermentative pH was pH 5 under submerged fermentation.