复合发酵棉籽粕营养价值及活性产物分析研究

旨在研究复合固态发酵(两株酵母和一株霉菌)对棉籽粕脱毒效果及营养价值的影响,同时分析测定发酵底物中的活性产物。结果表明:复合发酵可极显著降低棉籽粕底物游离棉酚含量(P0.01),降解率达71.90%;棉籽粕底物粗蛋白、总氨基酸和必需氨基酸含量分别提高28.96%、8.83%、7.58%;发酵54~60 h时底物中蛋白酶活力最高(酸性蛋白酶活力为931.58 U/g,中性蛋白酶活力为1 097.79 U/g,碱性蛋白酶活力为798.62 U/g),纤维素酶活力最高(滤纸酶活力为1 601.66 U/g,Cx酶活力为3 590.02 U/g,C1酶活力为1 685.35 U/g),淀粉酶活力最高为578.05 U/g;同时发酵过程产生了一定量的有机酸。     

DETECTION AND IDENTIFICATION OF LACTOBACILLUS LINDNERI FROM BREWERY ENVIRONMENTS

Ten detection media and six cultivation techniques were evaluated for the detection of a harmful brewery contaminant, for which the name Lactobacillus lindneri was recently revived. These bacteria showed slow and weak growth on solid media. However, enrichment of beer with NBB-C or the use of a mixture of MRS and beer (4:1 v/v) reduced the detection time by 2 days or more, depending on the strain, compared to cultivation on solid brewery media. Eight brewery isolates from different origins, the type strain and a test strain were characterized by carbohydrate fermentation tests (API 50 CHL), by a chemotaxonomical (SDS-PAGE) and by a genomic fingerprinting (ribotyping) method. The results obtained by all these methods indicated that the isolates studied form a single group and can be assigned to the species L. lindneri. However, using the current standard reagents, ribotyping cannot discriminate the strains isolated from different sources .     

Induction of Viable but Nonculturable State in Beer Spoilage Lactic Acid Bacteria

Strong beer spoilage strains Lactobacillus lindneri DSM 20692 and Lactobacillus paracollinoides JCM 11969^T were repeatedly subcultured in degassed beer and their culturability on MRS agar was examined. As a result, the two strains were found to show decreased culturability, suggesting that the prolonged contact with beer reduces the culturability of beer spoilage lactic acid bacteria (LAB). After 30 subcultures in degassed beer, both strains were subjected to sublethal heat treatment. As a consequence, L. lindneri DSM 20692 and L. paracollinoides JCM 11969^T were no longer detectable on MRS agar despite the presence of 460 viable cells, indicating that the viable but nonculturable (VNC) states were induced for both strains. Problematically, the heat treated VNC strains were shown to exhibit beer spoilage ability, suggesting that spoilage incidents can occur without detection by culture media. It was also shown that, once acquired, the VNC states are stably maintained in beer without further heat treatment. These results suggest the possibility that beer spoilage LAB strains remain hidden in pitching yeast and work‐in‐process products without detection. Furthermore L. lindneri DSM 20692 and L. paracollinoides JCM 11969^T in VNC states were successfully stored at ?80°C with 10% dimethyl‐sulfoxide as a cryoprotectant and reconstituted in degassed beer without losing VNC characteristics. Taken together, these findings show that valuable bioresources can be acquired from culturable beer spoilage LAB strains and maintained for long‐term storage as frozen culture stocks.