Yaovi Sylvestre Ahou

I study at the University of Nantes, IMT Atlantique Nantes & the University of Abomey-Calavi, Republic of Benin) In September 2019, thanks to BRISK2, I visited the Green Chemistry department at the Politecnico of Turin in Italy. My goal was to carry out the whole process of alcoholic fermentation of water hyacinth using the filamentous fungi (neurospora intermedia).  

The first step was to pre-treat the biomass under steam explosion condition (220°C, 23 bar, 15’) before processing to ethanol production. Due to the high temperature and pressure conditions, the hemicellulosic compounds were totally degraded, evidenced by the low carbohydrates contents of supernatant taken from the pre-treatment process.   

Despite a low sugar content, the fermentation process was performed for 96 hours. The anaerobic reactor was monitored daily by assaying glucose content and taking the pH of the fermentation broth. The results showed an increase of glucose content and a steady pH (approximately 6). The increase in glucose can be explained by the conversion of complex sugars (cellulose) into simple sugars by hydrolysis reaction performed my fungi strains.  

Ethanol measurement executed at a later date at my home laboratory in GEPEA/IMT Atlantique Nantes University, showed the presence of ethanol. This confirmed the feasibility of making ethanol from water hyacinth biomass at a large enough scale. 

In summary, bioethanol production of water hyacinth performed at the laboratory scale (GEPEA/IMT Atlantique) and the pilot scale research at the Politecnico of Turin shows the effectiveness of the pre-treatment.  

Results showed that water hyacinth requires less energy for pre-treatment, while for cassava peel, it was necessary to increase the temperature and lower the pH to break and solubilize lignin content in the peel. Furthermore, using filamentous strains resulted in simultaneous saccharification and fermentation without the need to add enzymes. In addition, using the filamentous strains throughout the whole ethanol process would result in lower investment cost (large scale) and make the process more environmentally friendly.