• SHASHI KUMAR

      Articles written in Journal of Biosciences

    • Metabolic engineering of chloroplasts for artemisinic acid biosynthesis and impact on plant growth

      Bhawna Saxena Mayavan Subramaniyan Karan Malhotra Neel Sarovar Bhavesh Shobha Devi Potlakayala Shashi Kumar

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      Chloroplasts offer high-level transgene expression and transgene containment due to maternal inheritance, and are ideal hosts for biopharmaceutical biosynthesis via multigene engineering. To exploit these advantages, we have expressed 12 enzymes in chloroplasts for the biosynthesis of artemisinic acid (precursor of artemisinin, antimalarial drug) in an alternative plant system. Integration of transgenes into the tobacco chloroplast genome via homologous recombination was confirmed by molecular analysis, and biosynthesis of artemisinic acid in plant leaf tissues was detected with the help of 13C NMR and ESI-mass spectrometry. The excess metabolic flux of isopentenyl pyrophosphate generated by an engineered mevalonate pathway was diverted for the biosynthesis of artemisinic acid. However, expression of megatransgenes impacted the growth of the transplastomic plantlets. By combining two exogenous pathways, artemisinic acid was produced in transplastomic plants, which can be improved further using better metabolic engineering strategies for commercially viable yield of desirable isoprenoid products.

    • Life cycle assessment of Chlorella species producing biodiesel and remediating wastewater

      PRACHI NAWKARKAR AMIT KUMAR SINGH MALIK ZAINUL ABDIN SHASHI KUMAR

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      Constantly rising energy demands, finite fossil fuel reserves and deteriorating environmental conditions have invokedworldwide interest to explore the sustainable sources of renewable biofuels. Locally adapted photosynthetic oleaginousmicroalgae with rapid growth on variable temperatures could be an ideal way for bioremediating the wastewater (WW) whileproducing the feedstock for biodiesel. To test this notion, an unknown strain was isolated from a sewage fed lake (Neela-Hauz).It was discerned as Chlorella sorokiniana-I using the 16S rDNA and 18S rDNA barcodes. The culture conditions such as pH,illumination, different temperature ranges and growth medium were cohesively optimized prior to the assessment of C.sorokiniana-I’s efficacy to remediate the WW and biodiesel production. The strain has thrived well up to 40 deg C when continuouslygrown for 15 days. The highest lipid accumulation and biomass productivity were recorded in 100%WW. Fatty acidmethyl ester (FAME) content was observed to be more than twice in WW (47%), compared to control synthetic media, TAP(20%) and BG11 (10%), which indicate the importance of this new isolate for producing economically viable biodiesel.Moreover, it is highly efficient in removing the total nitrogen (77%), total phosphorous (81%), iron (67%) and calcium (42%)from the WW. The quality of WW was considerably improved by reducing the overall chemical oxygen demand (48%),biological oxygen demand (47%) and alkalinity (15%). Thus, C. sorokiniana-I could be an ideal alga for the tropical countriesin the remediation of WW while producing feedstock for biodiesel in a cost-effective manner.

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