Seminars

Depleting fossil fuel reserves and growing demand for　energy have necessitated the renewed search for alternative energy resources　such as plants and algae. The first generation biofuels were produced from　starch and sugars (bioethanol) and from seed oils (biodiesel). These, however,　soon became negatively associated with issues such as competition with food　supply, significant land-use changes and several other ethical issues. The　production of second generation biofuels from lignocellulosic materials from　grasses and trees requires high-input saccahrificationtechnologies involving　extensive pre-treatments and expensive cellulolytic enzymes, adding to the high　costs of second generation bioethanol. Recently, third generation biofuels　derived from microalgae have attracted the attention of plant biologists and　industrialists due to fast growth rate, high CO2 fixation ability　and high production capacity of microalgae. Now, there also exists promising　fourth generation of biofuels on the horizon which involves　metabolically-engineering of plants and algae possessing traits such as high　biomass yield, improved feedstock quality and high CO2 fixation. In　recent years, efforts have been made via genetic engineering approaches for　improving saccharification of cell walls. This presentation will focus on　recent progress made in the alteration of cell wall properties through　manipulation of native cell wall genes for enhanced saccharification and　bioethanol production.Another use of plant biomass is for production of biodiesel.　Recently, we enhanced accumulation of fatty acids (FAs) in stems of transgenic　tobacco plants expressing Arabidopsis diacylglycerol acyltransferase 1 (DGAT1) and LEAFY COTYLEDON2 (LEC2) genes under a developing xylem-specific cellulose synthase promoter from aspen trees. The transgenic　tobacco plants accumulated significantly higher amounts of FAs in their stems.　On an average, DGAT1 and LEC2 overexpression showed a 63% and 80%　increase in total FA production in mature stems of transgenic plants over that　of controls, respectively. In LEC2　lines, the relative mRNA levels of the downstream genes encoding plastidic　proteins involved in FA synthesis and accumulation were also elevated. Thus we　provide a proof of concept for enhancing total energy yield per plant through　accumulation of higher levels of FAs in transgenic stems for biodiesel　production. The lignocellulosic material from stems can also be additionally used　for bioethanol production.