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Hu H, Qimu G, Nie J, Wu N, Dan T. Selection of a galactose-positive mutant strain of Streptococcus thermophilus and its optimized production as a high-vitality starter culture. J Dairy Sci 2024; 107:6558-6575. [PMID: 38754828 DOI: 10.3168/jds.2023-24550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 03/20/2024] [Indexed: 05/18/2024]
Abstract
Streptococcus thermophilus is a common starter in yogurt production and plays an important role in the dairy industry. In this study, a galactose-positive (Gal+) mutant strain, IMAU20246Y, was produced using the chemical mutagen N-methyl-N'-nitro-N-nitrosoguanidine (NTG) from wild-type S. thermophilus IMAU20246, which is known to have good fermentation characteristics. The sugar content of milk fermented by either the mutant or the wild type was determined using HPLC; metabolism of lactose and galactose was significantly increased in the mutant strain. In addition, we used response surface methodology to optimize components of the basic M17 medium for survival ratio of the mutant strain. Under these optimal conditions, the viable counts of mutant S. thermophilus IMAU20246Y reached 4.15 × 108 cfu/mL and, following freeze-drying in the medium, retained cell viability of up to 67.42%. These results are conducive to production of a high-vitality starter culture and development of "low sugar, high sweetness" dairy products.
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Affiliation(s)
- Haimin Hu
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Inner Mongolia Agricultural University, Hohhot 010018, China; Inner Mongolia Key Laboratory of Dairy Biotechnology and Engineering, Inner Mongolia Agricultural University, Hohhot 010018, China
| | - Gesudu Qimu
- Inner Mongolia Scitop Bio-tech Co. Ltd., Hohhot 011508, China
| | - Jiaying Nie
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Inner Mongolia Agricultural University, Hohhot 010018, China; Inner Mongolia Key Laboratory of Dairy Biotechnology and Engineering, Inner Mongolia Agricultural University, Hohhot 010018, China
| | - Na Wu
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Inner Mongolia Agricultural University, Hohhot 010018, China; Inner Mongolia Key Laboratory of Dairy Biotechnology and Engineering, Inner Mongolia Agricultural University, Hohhot 010018, China
| | - Tong Dan
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture and Rural Affairs, Inner Mongolia Agricultural University, Hohhot 010018, China; Inner Mongolia Key Laboratory of Dairy Biotechnology and Engineering, Inner Mongolia Agricultural University, Hohhot 010018, China.
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Abstract
TILLING is a method to find mutations in a gene of interest by scanning amplicons from a mutagenized population for sequence changes, commonly a single nucleotide. In the past 5 years, mutation detection by sequencing has become increasingly popular. This chapter details the experimental flow for TILLING-by-Sequencing, highlighting the critical steps involved in tridimensional pooling of genomic DNA templates, preparation of libraries for high-throughput sequencing, and bioinformatic processing of the sequence data.
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Affiliation(s)
- Helen Tsai
- Department of Plant Biology and Genome Center, University of California at Davis, One Shields Avenue, Davis, CA, 95616, USA
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