MICROBIAL isoprene production: an overview.

Isoprene, a volatile C5 hydrocarbon, is a precursor of synthetic rubber and an important building block for a variety of natural products, solely being produced by petrochemical routes. To mitigate the ever-increasing contribution of petrochemical industry to global warming through significant carbon (CO2) evolution, bio-based process for isoprene production using microbial cell factories have been explored. Highly efficient fermentation-based processes have been studied for little over a decade now with extensive research on the rational strain development for creating robust strains for commercial isoprene production. Most of these studies involved sugars as feedstocks and using naturally occurring isoprene pathways viz., mevalonate and methyl erythritol pathway in E. coli. Recent advances, driven by efforts in reducing environmental pollution, have focused on utilization of inorganic CO2 by cyanobacteria or syngas from waste gases by acetogens for isoprene production. This review endeavors to capture the latest relevant progress made in rational strain development, metabolic engineering and synthetic biology strategies used, challenges in fermentation process development at lab and commercial scale production of isoprene along with a future perspective pertaining to this area of research.

C/N Ratio and Specific Growth Rate Plays Important Role on Enhancing Isoprene Production in Recombinant Escherichia coli.

Effect of fermentation parameters such as C/N ratio, specific growth rate, phosphate limitation, and plasmid instability on enhancing isoprene production is the focus of the current study. Isoprene productivity in the recombinant Escherichia coli K12_MVA strain showed a bell-shaped relationship with specific growth rate in bioreactor studies with isoprene volumetric productivity peaking at 0.35/h. This behavior was depicted by a production inhibition kinetic model which envisaged a serious competition between the cellular growth, acetic acid production, and isoprene biosynthesis. The model equation derived showed a reasonable fit with the experimental values. Judicious control of the growth rates and acetate accumulation by optimizing C/N ratio, phosphate concentration, and intermittent feeding strategy resulted in maximizing the carbon flux towards isoprene. Plasmid instability caused by metabolic burden posed by the presence of dual plasmids on the bacteria was simulated using first-order degradation kinetics. The experimental plasmid loss trend was in accordance with the model simulated trend, where higher plasmid loss correlated with higher specific growth rates. Modulating the growth rate, acetate accumulation, and plasmid instability resulted in achieving maximum isoprene volumetric productivity of 1.125 g/l/h with 46.67% of carbon flux towards isoprene and a isoprene titre of 18 g/l in 16 h fermentation run.

Evaluation of quality and efficacy of an ethnomedicinal plant Ageratum conyzoides L. in the management of pediculosis.

BACKGROUND: Infestation with the head louse, Pediculus humanus capitis, is one of the most common parasitic infestations of human worldwide. Traditionally, the main treatment for control of head lice is chemical control that includes wide variety of neurotoxic synthetic insecticides. The main difficulty posed in controlling the head louse infestation is increasing lice resistance to synthetic pediculicidal drugs. Plant-based drugs; especially essential oil components and standardized extracts have been suggested as an alternative source of materials for insect control. Ageratum conyzoides L. (Asteraceae) has been reported to possess antifungal and insecticidal properties. In the present research work, an attempt has been made to evaluate in vitro pediculicidal activity of A. conyzoides. METHODS: A filter paper diffusion bioassay was carried out in order to determine the pediculicidal activity of different extracts of A. conyzoides. RESULTS: The study elucidates the active plant part and suitable extract responsible for the therapeutic efficacy of this plant in the management of pediculosis. CONCLUSION: Findings of the present study indicate the potential of A. conyzoides extract to be included in the formulations as a pediculicidal agent.