{'fraction_non_alphanumeric': 0.02548476454293629, 'fraction_numerical': 0.002770083102493075, 'mean_word_length': 5.7388059701492535, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Production of Recombinant α-Galactosidases inThermus thermophilus

ABSTRACT A Thermus thermophilus selector strain for production of thermostable and thermoactive α-galactosidase was constructed. For this purpose, the native α-galactosidase gene (agaT) ofT. thermophilus TH125 was inactivated to prevent background activity. In our first attempt, insertional mutagenesis ofagaT by using a cassette carrying a kanamycin resistance gene led to bacterial inability to utilize melibiose (α-galactoside) and galactose as sole carbohydrate sources due to a polar effect of the insertional inactivation. A Gal+ phenotype was assumed to be essential for growth on melibiose. In a Gal−background, accumulation of galactose or its metabolite derivatives produced from melibiose hydrolysis could interfere with the growth of the host strain harboring recombinant α-galactosidase. Moreover, the AgaT− strain had to be Kms for establishment of the plasmids containing α-galactosidase genes and the kanamycin resistance marker. Therefore, a suitable selector strain (AgaT− Gal+ Kms) was generated by applying integration mutagenesis in combination with phenotypic selection. To produce heterologous α-galactosidase in T. thermophilus, the isogenes agaA and agaBof Bacillus stearothermophilus KVE36 were cloned into anEscherichia coli-Thermus shuttle vector. The region containing the E. coli plasmid sequence (pUC-derived vector) was deleted before transformation of T. thermophilus with the recombinant plasmids. As a result, transformation efficiency and plasmid stability were improved. However, growth on minimal agar medium containing melibiose was achieved only following random selection of the clones carrying a plasmid-based mutation that had promoted a higher copy number and greater stability of the plasmid.