Ethanol production from orange peels: two-stage hydrolysis and fermentation studies using optimized parameters...

Area of Science:

• Biotechnology
• Biochemical Engineering
• Renewable Energy

Background:

• Orange peel powder (OPP) is an abundant lignocellulosic waste material.
• Efficient conversion of OPP into biofuels like ethanol is crucial for sustainable energy production.
• Optimizing pretreatment and fermentation conditions is key to maximizing ethanol yields.

Purpose of the Study:

• To evaluate orange peels as a fermentation feedstock for enhanced ethanol production.
• To determine optimal process conditions for hydrolysis and fermentation of OPP.
• To achieve high ethanol yields and productivity from OPP hydrolysate.

Main Methods:

• Primary hydrolysis of OPP using varying acid concentrations (0-1.0%) at 121°C.
• Secondary hydrolysis of pretreated biomass at 0.5% acid concentration.
• Response Surface Methodology (RSM) to optimize pH, temperature, and fermentation time.
• Validation of optimized parameters in a 2 L batch fermenter.

Main Results:

• Optimal primary hydrolysis achieved at 0.5% acid concentration to minimize inhibitory compounds.
• RSM optimization identified ideal fermentation parameters: pH 5.4, 34°C, and 15 hours.
• Fermentation in a 2 L batch fermenter yielded 0.25 g/g (biomass basis) and 0.46 g/g (substrate-consumed basis) ethanol.
• Achieved a volumetric ethanol productivity of 3.37 g/L/h.

Conclusions:

• Orange peel powder is a viable feedstock for ethanol production.
• Optimized hydrolysis and fermentation significantly enhance ethanol yields and productivity.
• The developed process shows potential for industrial-scale bioethanol production from citrus waste.