Effect of Artificial Diet Modification with Dextrose on the Growth and Fatty Acid Composition of Tenebrio molitor Larvae for Biodiesel Production

Tenebrio molitor larvae are a promising source for the next generation of liquid biofuels. However, the conditions and processes required for rearing this insect for biodiesel production need to be investigated. In this study, the effect of dextrose addition to an artificial diet in the oil and biodiesel yield was evaluated. Larvae were fed artificial diets modified with 3, 6, 9, and 15% dextrose. Survival rate, mean dry weight, and oil yield were registered. The 15% dextrose addition resulted in 75% survival, 25 mg individual dry weight, and 29% oil yield. The main components of this oil were palmitic acid (14%), oleic acid (37%), and linoleic acid (20%). With the addition of dextrose, the total saturated fatty acids increased 13% and the polyunsaturated fatty acids decreased 16% compared to the control. However, with the transesterification reaction, the fatty acid methyl esters remained similar for both treatments, with methyl oleate, methyl linoleate, and methyl linolenate as major components. This suggest that the transesterification reaction was incomplete, due to the oil/methanol ratio or the catalyst. Thus, even though a more balanced saturated/unsaturated fatty acid profile can be achieved through dextrose addition, another transesterification method should be tested to obtain a complete reaction.