Nitrile hydratase mediated green synthesis of lactamide by immobilizing Rhodococcus pyridinivorans NIT-36 cells on N, N'-Methylene bis-acrylamide activated chitosan

In this paper green synthesis of an important commodity chemical lactamide has been undertaken using chitosan immobilized Rhodococcus pyridinivorans NIT-36 harbouring nitrile hydratase (NHase) enzyme. The cells immobilization (300 mg/g) is based on the partial entrapment of cells by suspension cross-linking technique facilitated by N, N'-Methylene bis-acrylamide. In the repeated-use experiments, the immobilized cells retained 80% of its initial activity when stored at 4 °C for 30 days. NHase activity of free and immobilized cells was studied over temperature ranging from 25 °C to 60 °C. The activity for free cells showed a sharp decline of 70% when the reaction temperature was elevated from 45 °C to 50 °C whereas chitosan immobilized cells retained their activity in the same temperature range. A fed-batch reaction was designed and the immobilized cells showed 100% similar enzymatic pattern for five consecutive rounds which gradually decreased in following cycles. A volumetric productivity of 20 g/L and catalytic productivity of 8.33 g/g dcw/h for lactamide were achieved.

Random Mutagenesis of Thermophilic Xylanase for Enhanced Stability and Efficiency Validated through Molecular Docking

BACKGROUND

Xylanases of thermophilic origin are more robust and stable and hence more suitable for industrial applications. The aim of the research was to develop a patent using a robust mutant exhibiting enhanced xylanase activity. The strain (Bacillus aestuarii SC-2014) subjected to mutagenesis is thermophilic in origin and hence it is envisioned that the enhancement of its catalytic potential will enhance its industrial applicability.

OBJECTIVE

The main aim was to develop a stable and vigorous mutant having higher xylanase activity and improved thermostability.

METHODS

The bacterial strain isolated from the Tattapani hot springs of Himachal Pradesh (India) was mutagenized by single separate exposure of Ethyl methane sulphonate (EMS) and N-methyl N-nitro N-nitrosoguanidine (MNNG).

RESULTS

A mutant library was generated and extensive screening led to the identification of the most potent mutant strain selected and designated as Bacillus sp. SC-2014 EMS200 (MTCC number 25046) which displayed not only enhanced xylanase activity and thermo stability but also appreciable genetic stability. This strain displayed a 3-fold increase in enzyme activity and simultaneously, a significant reduction in fermentation time from 72 h to 48 h was also observed. The xylanase gene from wild and mutant strain was cloned, sequenced and subjected to molecular docking. Two mutations H121D and S123T were present inside the binding pocket.

CONCLUSION

Mutation H121D made the binding pocket more acidic and charged, thus enhancing the xylanase activity for mutant protein. Mutations also resulted in charged amino acids (Y99K and H121D) which were identified as a probable cause for enhancing the thermostability of mutant protein.

Restriction enzyme-mediated insertional mutagenesis: an efficient method of Rosellinia necatrix transformation

Rosellinia necatrix: causing root rot disease is a very destructive pathogen of woody plants and is responsible for yield losses to a large number of fruit trees. The genetic analysis of this pathogen has not been picked up because of difficulty in generating mutations in Rosellinia necatrix for many reasons. A number of methods have been proposed for inducing mutations in Rosellinia necatrix but none of them proved worth because of very low transformation efficiencies. Here, we propose an efficient method for Rosellinia necatrix protoplast production, where protoplasts in the tune of 10⁷ per ml can be easily generated. We also propose a restriction enzyme-mediated integration (REMI)-based methods for efficient transformation of Rosellinia necatrix. In the present study, an approximate of 800 transformants was obtained from 5 μg of linearized plasmid. Out of 47 single spored transformants analyzed, only 33 showed hygromycin gene amplification using PCR and only 19 transformants showed single gene integration in southern hybridization, which accounted for single gene integration percentage of 42%, highest amongst all the previous reports on Rosellinia necatrix transformations. Some of the transformants studied for pathogenicity phenotype also showed a marked reduction in pathogenicity. Thus, in the present investigation, 42% single gene integrations among the transformed colonies can be considered as excellent transformation efficiency.