Design and optimization of a sono-hybrid process for bioethanol production from Parthenium hysterophorus

• This study presents a process of bioethanol production from Parthenium hysterophorus.
• 3-step process involves pretreatment, enzymatic hydrolysis and fermentation.
• Ethanol yield from pentose and hexose sugars was 0.32 and 0.41 g/g, respectively.
• Overall ethanol yield of 0.26 g/g raw biomass is at par with other reported biomass.
• 18-fold enhancement of kinetics of enzymatic hydrolysis by ultrasound was attained.

This paper presents a laboratory scale process for production of bioethanol from Parthenium hysterophorus. This process consists of three steps, viz. biomass pretreatment, enzymatic hydrolysis of pretreated biomass and fermentation of pentose and hexose hydrolyzates obtained from acid pretreatment and enzyme hydrolysis, respectively. The step of enzyme hydrolysis has been optimized using response surface methodology for concentrations of the enzymes and the concentration of biomass. The optimum parameters were: biomass concentration = 4.212% (w/v), cellulase concentration = 135.86 FPU/g substrate and cellobiase concentration = 75 U/g substrate. Use of ultrasound during enzymatic hydrolysis at optimized conditions resulted in a marked 18-fold enhancement in the kinetics of hydrolysis. Fermentation of the pentose hydrolyzate with Candida shehatae NCIM 3500 resulted to ethanol yield of 0.069 g/g raw biomass, while fermentation of the enzymatic hydrolyzate with Saccharomyces cerevisiae MTCC 170 resulted to an ethanol yield of 0.187 g/g raw biomass. The total ethanol yield from fermentation of pentose and hexose hydrolyzates was 0.26 g/g raw biomass. This process also provides a potential solution to effective utilization of the noxious waste biomass of P. hysterophorus.