Temperature‐induced mutagenesis‐based adaptive evolution of Bacillus amyloliquefaciens for improving the production efficiency of menaquinone‐7 from starch

Abstract

BACKGROUND Starch can be used as a carbon source for producing menaquinone‐7 (MK‐7) by Bacillus sp., but the final titer and productivity are unsatisfactory because starch cannot be effectively hydrolyzed to fermentable sugars. This article focuses on developing thermo‐tolerable MK‐7 high‐producing strains by temperature‐induced mutagenesis‐based adaptive evolution. RESULTS Here, we isolated a thermo‐tolerable MK‐7 high‐producing strain B. amyloliquefaciens MK50‐36 after multi‐rounds of acclimation at high temperature. Strain MK50‐36 showed a large growth with soluble starch as carbon source at 50 °C. Compared with the parental strain B. amyloliquefaciens H.β.D.R.‐5 cultivated at 37 °C, MK‐7 yield of strain MK50‐36 increased about twofold at 50 °C when soluble starch was used as the sole carbon resource (17.5 ± 1.5 mg L–1 versus 37.1 ± 2.1 mg L–1). In addition, strain MK50‐36 showed an improvement in starch utilization rate as compared with strain H.β.D.R.‐5 because α‐amylase activity of strain MK50‐36 was the highest at 50 °C. Moreover, MK‐7 yield of strain MK50‐36 was further increased by feeding fresh broth to control the amount of fermentation liquid in fed‐batch fermentation because fermentation broth will be easy to volatilize and thus affect the production of MK‐7 at high temperature, which reached up to 52.7 ± 4.6 mg L–1. CONCLUSION These results indicated that soluble starch can act as an effective carbon source for producing MK‐7, and strain MK50‐36 has a superior capacity to produce MK‐7 from soluble starch. © 2020 Society of Chemical Industry

Production of Vitamin K by Wild-Type and Engineered Microorganisms

“…Recently, Liu, N. et al (2021) used the H.β.D.R.-5 mutant to create another B. amyloliquefaciens mutant having a high α-amylase activity through adaptive evolution by temperature-induced mutagenesis at a high growth temperature. The resulting heat-resistant mutant MK50-36 produced 57 mg/L of MK-7 in corn starch medium for 6 days of fed-batch fermentation [ 90 ].…”

Enhancing menaquinone-7 biosynthesis by adaptive evolution of Bacillus natto through chemical modulator

“…Under certain stress conditions, microorganisms could enrich the favorable genetic changes brought by the specific pressure during the successive cultivation (Espinosa et al 2020). Liu et al obtained a high-temperature resistant Bacillus amyloliquefaciens through long-term high-temperature cultivation and the MK-7 yield of the strain was improved by 2 times at 50 °C using starch as the sole carbon source (Liu et al 2021). Besides, a sequential cultivation of the C5-utilizing Bacillus coagulans with ethanol resulted in 2.6-fold increase in lactic acid yield (Cubas-Cano et al 2020).…”