Influence of hydroxypropyl-β-cyclodextrin on phytosterol biotransformation by different strains of Mycobacterium neoaurum

Abstract

Cyclodextrins (CDs) can improve productivity in the biotransformation of steroids by increasing conversion rate, conversion ratio, or substrate concentration. However, little is known of the proportion of products formed by multi-catabolic enzymes, e.g., via sterol side chain cleavage. Using three strains with different androst-1,4-diene-3,17-dione (ADD) to androst-4-ene-3,17-dione (AD) ratios, Mycobacterium neoaurum TCCC 11028 (MNR), M. neoaurum TCCC 11028 M1 (MNR M1), and M. neoaurum TCCC 11028 M3 (MNR M3), we found that hydroxypropyl-β-cyclodextrin (HP-β-CD) can appreciably increase the ratio of ADD to AD, the reaction rate, and the molar conversion. In the presence of HP-β-CD, conversion of 0.5 g/L of phytosterol (PS) was 2.4, 2.4, and 2.3 times higher in the MNR, MNR M1, and MNR M3 systems, respectively, than in the controls. The ADD proportion increased by 38.4, 61.5, and 5.9 % compared with the control experiment, which resulted in a strong shift in the ADD/AD ratio in the ADD direction. Our results imply that the three PS-biotransforming strains cause efficient side chain degradation of PS, and the increased conversion of PS when using HP-β-CD may be associated with the higher PS concentration in each case. A similar solubilizing effect may not induce a prominent influence on the ADD/AD ratio. However, the different activities of the Δ¹-dehydrogenase of PS-biotransforming strains result in different incremental percentage yields of ADD and ADD/AD ratio in the presence of HP-β-CD.

Side-chain cleavage of phytosterols byMycobacteriumsp. MB 3683 in a biphasic ionic liquid/aqueous system

“…One of the problems is the low solubility of sterols in aqueous systems that results in poor availability of substrate to whole‐cell biocatalysts; the other is the inhibition of the side‐chain degradation process caused by the product AD(D) . Generally, the problem of low solubility can be partially relieved by strategies of micronization of substrate to fine particles, surfactant facilitated emulsification, water‐miscible co‐solvents, cyclodextrins, or application of biphasic systems . Product inhibition may be solved by selection of strains tolerant to high concentrations of steroid product or in situ product removal (ISPR) that can also be carried out in biphasic systems …”

Influence of temperature on nucleus degradation of 4-androstene-3, 17-dione in phytosterol biotransformation by Mycobacterium sp.

“…; Shen et al . ). However, little emphasis has been placed on how to reduce the decomposition of products in the process of biotransformation of phytosterols.…”

“…Several Letters in Applied Microbiology 61, 63--68 © 2015 The Society for Applied Microbiology significant gene clusters involved in the transformation of sterols were also identified in recent years, leading to the modification of target genes to reduce the production of by-products (Song et al 2010;Yao et al 2014). Furthermore, two-phase systems and cyclodextrins have been used to increase the solubility of steroid substrates in the aqueous phase (Donova et al 2007;Shen et al 2012). However, little emphasis has been placed on how to reduce the decomposition of products in the process of biotransformation of phytosterols.…”

Mutation breeding of high 4-androstene-3,17-dione-producing Mycobacterium neoaurum ZADF-4 by atmospheric and room temperature plasma treatment

“…In Mycobacterium, the microbial catabolic pathway of phytosterols is so complex that metabolic engineering with a rational design is very difficult. Recently, studies of Mycobacterium strains have reported that the solubility of phytosterols can be increased by adding hydroxypropyl-β-cyclodextrin (HP-β-CD) (Shen et al, 2012). This approach has been used for improving steroid biotransformation in aqueous media in strain ZJUVN-08 of M. neoaurum (Zhang X.Y.…”