The disclosure encompassed herein relates, in part, to a method for increasing energy density of plant biomass that can be used for production of renewable fuel, such as biodiesel oil and/or ethanol. In an aspect, genetic engineering for enhanced sugar accumulation can be achieved by overexpressing a bacterial enzyme sucrose isomerase. Sugars or oils extracted from the plants of the disclosure encompassed herein may be used for industrial purposes such as heating, producing bio-fuels such as biodiesel fuel, or lubricating applications.