淀粉基二十二碳六烯酸菌种的构建轻工技术与工程发酵专业论文.docxVIP

ABSTRACTDocosahexaenoic ABSTRACT Docosahexaenoic acid is a necessary polyunsaturated fatty acid for human body． Currently,Schizochytrium sp．is a kind of bright market prospects DHA—rich microbial resources which has the characteristics of high content of DHA，fast growth，easy to culture， non．toxic to humans and animals．It has been mainly focused on glucose as carbon source for DHA production．Starch is higher yield and cheaper than glucose。Thus，if a superior DHA rich strain using starch as carbon source has been found，it will greatly simplify the production process and reduce the production costs．In this study,a DHA rich strain using starch as carbon source was produced by protoplast fusion of Schizoch)7trium B4D 1 and Aspergillus niger． The optimized condition for preparation of protoplasts from Schizochytrium and AspergiUus niger were as follows：the lysing enzyme concentration were 5mg／mL，the incubation time were 36h and 1 5h，enzymolysised for 30min and 1 50min．The protoplasts fomation rate were 92．4％and 1．25x 106，the regeneration rate were 58．8％and 22．8％， respectively．We inactivated Protoplasts ofAspergillus niger as a genetic marker,and used the characteristics of Schizochytrium which could not take advantage of starch．The fusion rate reached 3．1％for about 30。C and 1 0 min with the 40％PEG6000 used as fusion agents· The fusants were prescreened according to colony morpholagical character,screened again with strains lipid yield in starch sodium as sole carbon source for fermentation． 乃e RAPD result showed that there was genetic recombination occurred between B4D1 and CGMCC 3．316．M．3 have specific gene of Schizoch多’trium and A·niger． H∞w徭蹦it has more genetic information from B4D1．And it still remain stable after 1 0 generation’S culture． The transcriptome library of Schizochytrium contained 2 1 582 1 3 Contigs which were assembled after filtering the Reads，and the 3 1 930 Unigenes were obtained by assembling the ContigS．To compare between Unigenes and the COG datab