Smita Srivastava

Bio: Smita Srivastava is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Azadirachtin & Hairy root culture. The author has an hindex of 15, co-authored 40 publications receiving 998 citations. Previous affiliations of Smita Srivastava include Indian Institute of Technology Delhi & Indian Institutes of Technology.

Biotechnology and Genetic Engineering for Alkaloid Production 8

Abstract: Alkaloidsarea diverse group ofcomplexorganic moleculesfoundin about20% of plant species in small quantities. Their potent biological activity has led to their exploitation as pharmaceuticals, stimulants, narcotics, and poisons. Despite their

Callus and cell suspension culture of Viola odorata as in vitro production platforms of known and novel cyclotides

Abstract: Cyclotides are unique plant cyclic-peptides that can serve as agrochemicals, pharmaceutical scaffolds for drug delivery, and therapeutic agents. Currently, cyclotides are obtained only via direct extraction from limited plants. Hence, they serve as valuable candidates for synthesis via plant cell bioprocesses. In this study, callus lines (47 in total) were successfully induced from the leaf and petiole explants of the Indian medicinal plant, V. odorata, on a solidified woody plant medium (WPM) supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) (4.5 mg/l). Two fast growing callus lines, VOP-4 and VOL-44, were selected for the development of cell suspension cultures having a doubling time of 8 and 6 days, respectively. Further, known (15) and novel (9) cyclotides were identified for the first time in the callus and cell suspension cultures of V. odorata, using liquid chromatography and Fourier transform mass spectrometry. The cyclotides were identified based on their monoisotopic mass (2.5–4 kDa), hydrophobic nature, disulfide bonds, circular structure and amino acid sequence. Some of the cyclotides identified in the study (vodo I96, vodo I97, vodo I98) were exclusively produced in callus/cell suspension cultures and not in the parent plant. The study revealed that besides germplasm conservation, plant cell bioprocessing of V. odorata could be a potential alternative for in vitro production of known and novel cyclotides.

Strategies to Overcome Oxygen Transfer Limitations During Hairy Root Cultivation of Azadiracta indica for Enhanced Azadirachtin Production

Abstract: The vast untapped potential of hairy root cultures as a stable source of biologically active chemicals has focused the attention of scientific community toward its commercial exploitation. However, the major bottleneck remains its successful scale-up. Due to branching, the roots form an interlocked matrix that exhibits resistance to oxygen transfer. Thus, present work was undertaken to develop cultivation strategies like optimization of inlet gas composition (in terms of % (v/v) O(2) in air), air-flow rate and addition of oxygen vectors in the medium, to curb the oxygen transfer limitations during hairy root cultivation of Azadirachta indica for in vitro azadirachtin (a biopesticide) production. It was found that increasing the oxygen fraction in the inlet air (in the range, 20-100% (v/v) O(2) in air) increased the azadirachtin productivity by approximately threefold, to a maximum of 4.42 mg/L per day (at 100% (v/v) O(2) in air) with respect to 1.68 mg/L per day in control (air with no oxygen supplementation). Similarly, increasing the air-flow rate (in the range, 0.3-2 vvm) also increased the azadirachtin productivity to a maximum of 1.84 mg/L per day at 0.8 vvm of air-flow rate. On the contrary, addition of oxygen vectors (in the range, 1-4% (v/v); hydrogen peroxide, toluene, Tween 80, kerosene, silicone oil, and n-hexadecane), decreased the azadirachtin productivity with respect to control (1.76 mg/L per day).

Production of bioactive cyclotides: a comprehensive overview

Abstract: Cyclotides are an emerging class of disulfide-rich plant cyclic peptides, believed to be present in plants for defence purposes. Their exceptional thermal, chemical and enzymatic stabilities make them suitable as therapeutic agents, agrochemicals, molecular imaging probes and pharmaceutical scaffolds for drug delivery. Nearly 350 cyclotides have been identified and reported to date, while more than 150,000 diverse cyclotides are estimated to occur in plants. With the current chemical identification methodologies, cyclotides can be identified even from crude extracts. This review will extensively describe the latest strategies pertaining to the screening of plants for the presence of cyclotides. Although identification of cyclotides in plants will help to explore their distribution, evolution, diversity and biological activities, natural plant extraction is not a sustainable and reliable method of such plant metabolite production. This can be attributed to several reasons such as inconsistent and non- uniform supply due to geographical and climatic conditions. Moreover, extraction of metabolites from the non-native, rare and endangered plant is not sustainable. Therefore, in vitro production technologies independent of the natural source availability are being explored to facilitate commercial applications of cyclotides. Owing to the complex structure, the chemical synthesis and recombinant microorganism-based methods of production provide limited yields of cyclotides. Production of biopharmaceutical peptides in plant cell cultures is a safe and commercially applicable alternative which can overcome some of these challenges. Hence, strategies for sustainable production of cyclotides by plant in vitro systems is discussed in-depth in this review.

Carbon flow in the rhizosphere: carbon trading at the soil–root interface

Abstract: The loss of organic and inorganic carbon from roots into soil underpins nearly all the major changes that occur in the rhizosphere. In this review we explore the mechanistic basis of organic carbon and nitrogen flow in the rhizosphere. It is clear that C and N flow in the rhizosphere is extremely complex, being highly plant and environment dependent and varying both spatially and temporally along the root. Consequently, the amount and type of rhizodeposits (e.g. exudates, border cells, mucilage) remains highly context specific. This has severely limited our capacity to quantify and model the amount of rhizodeposition in ecosystem processes such as C sequestration and nutrient acquisition. It is now evident that C and N flow at the soil–root interface is bidirectional with C and N being lost from roots and taken up from the soil simultaneously. Here we present four alternative hypotheses to explain why high and low molecular weight organic compounds are actively cycled in the rhizosphere. These include: (1) indirect, fortuitous root exudate recapture as part of the root’s C and N distribution network, (2) direct re-uptake to enhance the plant’s C efficiency and to reduce rhizosphere microbial growth and pathogen attack, (3) direct uptake to recapture organic nutrients released from soil organic matter, and (4) for inter-root and root–microbial signal exchange. Due to severe flaws in the interpretation of commonly used isotopic labelling techniques, there is still great uncertainty surrounding the importance of these individual fluxes in the rhizosphere. Due to the importance of rhizodeposition in regulating ecosystem functioning, it is critical that future research focuses on resolving the quantitative importance of the different C and N fluxes operating in the rhizosphere and the ways in which these vary spatially and temporally.

Bioconversion of lignocellulosic biomass: biochemical and molecular perspectives

Abstract: In view of rising prices of crude oil due to increasing fuel demands, the need for alternative sources of bioenergy is expected to increase sharply in the coming years. Among potential alternative bioenergy resources, lignocellulosics have been identified as the prime source of biofuels and other value-added products. Lignocelluloses as agricultural, industrial and forest residuals account for the majority of the total biomass present in the world. To initiate the production of industrially important products from cellulosic biomass, bioconversion of the cellulosic components into fermentable sugars is necessary. A variety of microorganisms including bacteria and fungi may have the ability to degrade the cellulosic biomass to glucose monomers. Bacterial cellulases exist as discrete multi-enzyme complexes, called cellulosomes that consist of multiple subunits. Cellulolytic enzyme systems from the filamentous fungi, especially Trichoderma reesei, contain two exoglucanases or cellobiohydrolases (CBH1 and CBH2), at least four endoglucanases (EG1, EG2, EG3, EG5), and one β-glucosidase. These enzymes act synergistically to catalyse the hydrolysis of cellulose. Different physical parameters such as pH, temperature, adsorption, chemical factors like nitrogen, phosphorus, presence of phenolic compounds and other inhibitors can critically influence the bioconversion of lignocellulose. The production of cellulases by microbial cells is governed by genetic and biochemical controls including induction, catabolite repression, or end product inhibition. Several efforts have been made to increase the production of cellulases through strain improvement by mutagenesis. Various physical and chemical methods have been used to develop bacterial and fungal strains producing higher amounts of cellulase, all with limited success. Cellulosic bioconversion is a complex process and requires the synergistic action of the three enzymatic components consisting of endoglucanases, exoglucanases and β-glucosidases. The co-cultivation of microbes in fermentation can increase the quantity of the desirable components of the cellulase complex. An understanding of the molecular mechanism leading to biodegradation of lignocelluloses and the development of the bioprocessing potential of cellulolytic microorganisms might effectively be accomplished with recombinant DNA technology. For instance, cloning and sequencing of the various cellulolytic genes could economize the cellulase production process. Apart from that, metabolic engineering and genomics approaches have great potential for enhancing our understanding of the molecular mechanism of bioconversion of lignocelluloses to value added economically significant products in the future.

Stress and defense responses in plant secondary metabolites production

Abstract: In the growth condition(s) of plants, numerous secondary metabolites (SMs) are produced by them to serve variety of cellular functions essential for physiological processes, and recent increasing evidences have implicated stress and defense response signaling in their production. The type and concentration(s) of secondary molecule(s) produced by a plant are determined by the species, genotype, physiology, developmental stage and environmental factors during growth. This suggests the physiological adaptive responses employed by various plant taxonomic groups in coping with the stress and defensive stimuli. The past recent decades had witnessed renewed interest to study abiotic factors that influence secondary metabolism during in vitro and in vivo growth of plants. Application of molecular biology tools and techniques are facilitating understanding the signaling processes and pathways involved in the SMs production at subcellular, cellular, organ and whole plant systems during in vivo and in vitro growth, with application in metabolic engineering of biosynthetic pathways intermediates.

In vitro plant tissue culture: means for production of biological active compounds

Abstract: Plant tissue culture as an important tool for the continuous production of active compounds including secondary metabolites and engineered molecules. Novel methods (gene editing, abiotic stress) can improve the technique. Humans have a long history of reliance on plants for a supply of food, shelter and, most importantly, medicine. Current-day pharmaceuticals are typically based on plant-derived metabolites, with new products being discovered constantly. Nevertheless, the consistent and uniform supply of plant pharmaceuticals has often been compromised. One alternative for the production of important plant active compounds is in vitro plant tissue culture, as it assures independence from geographical conditions by eliminating the need to rely on wild plants. Plant transformation also allows the further use of plants for the production of engineered compounds, such as vaccines and multiple pharmaceuticals. This review summarizes the important bioactive compounds currently produced by plant tissue culture and the fundamental methods and plants employed for their production.