Bioethanol production from Tunisian macroalgal biomass

The valorization of marine macroalgal biomass is among the most promising international programs focusing on the sustainable exploitation of marine environment. However, macroalgal biomass remains unexploited in Tunisia, even though it represents a highly abundant renewable biomass. The excessive proliferation of several algal species causes severe environmental disorders. The objective of this work is to study the potential use of macroalgae as biofuels feedstock in the Mediterranean region and particularly in Tunisia. This study focuses on certain macroalgal species collected from Bizerte and Tunis lagoons (e.g., Chaetomorpha linum, Enteromorpha intestinalis, Gracillaria gracillis, Ulva rigida, Gracillaria verrucosa, Cystoseira brachycarpa, Laurencia obtusa, Cystoseira sedoides, and Dictyopteris polypodioides). The macroalgae's biochemical composition was determined in a way that maximizes its valorization. To achieve this objective, a process of three steps was performed. First, the macroalgal biomass was pretreated by dilute sulfuric acid. Then, an enzymatic saccharification was performed to produce fermentable sugars. Finally, the obtained sugars were converted into bioethanol using Saccharomyces cerevisiae yeast. In fact, our experiments show that the maximum protein content of 16.22% +/- 0.270 was obtained with G. verrucosa, whereas the maximum carbohydrates content of 58.46% +/- 1.52% was obtained with D. polypodoies. This leads us to believe that macroalgae constitute a potential source of fiber and proteins. After a sulfuric acid pretreatment. The maximum reducing sugars and bioethanol yields were obtained, respectively, were of 324.6 mg/gDM (dry matter) and 0.24 g/gDM.