The　medium-temperature　alpha-amylase　of　Bacillus　amyloliquefaciens　is　widely　used　in　the　food　and　washing　process.　Enhancing　the　thermostability　of　alpha-amylases　and　investigating　the　mechanism　of　stability　are　important　for　enzyme　industry　development.　The　optimal　temperature　and　pH　of　the　wild-type　BAA　and　mutant　MuBAA　(D28E/V118A/S187D/K370　N)　were　all　60　degrees　C　and　6.0,　respectively.　The　mutant　MuBAA　showed　better　thermostability　at　50　degrees　C　and　60　degrees　C,　with　a　specific　activity　of　206.61　U/mg,　which　was　99.1%　greater　than　that　of　the　wild-type.　By　analyzing　predicted　structures,　the　improving　thermostability　of　the　mutant　MuBAA　was　mainly　related　to　enhanced　stabilization　of　a　loop　region　in　domain　B　via　more　calcium-binding　sites　and　intramolecular　interactions　around　Asp187.　Furthermore,　additional　intramolecular　interactions　around　sites　28　and　370　in　domain　A　were　also　beneficial　for　improving　thermostability.　Additionally,　the　decrease　of　steric　hindrance　at　the　active　cavity　increased　the　specific　activity　of　the　mutant　MuBAA.　Improving　the　thermostability　of　BAA　has　theoretical　refer-ence　values　for　the　modification　of　alpha-amylases.　(c)　2023　Elsevier　Inc.　All　rights　reserved.