Potential of bioethanol production from olive mill solid wastes

Area of Science:

• Biotechnology
• Microbiology
• Sustainable Energy

Background:

• Olive mill solid wastes (OMSW) are a lignocellulosic byproduct with potential for bioethanol production.
• Fermentation of pentose sugars like xylose is crucial for efficient biofuel generation from such wastes.

Purpose of the Study:

• To screen endogenous microorganisms from OMSW capable of fermenting pentoses and producing ethanol.
• To evaluate the efficiency of different fermentation strategies for bioethanol production from OMSW.

Main Methods:

• Isolation and identification of yeast strains from OMSW.
• Adaptation of yeast strains for improved fermentation performance.
• Separate Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF) processes were employed.
• Analysis of xylose utilization, xylitol, and ethanol production.

Main Results:

• Two yeast strains, *Issatchenkia orientalis* and *Pichia galeiformis/manshurica*, were identified.
• All tested strains could utilize xylose and produce xylitol, but not ethanol directly from xylose.
• *I. orientalis* showed improved ethanol production when supplemented with glucose in a separate hydrolysis and fermentation process.
• The simultaneous saccharification and fermentation process yielded an average of 3 g ethanol per 100 g dry OMSW.

Conclusions:

• While yeasts from OMSW can metabolize xylose, direct efficient ethanol production from pentoses remains a challenge.
• Current bioethanol yields from OMSW using the studied methods are not economically viable, despite the low cost of the raw material.