Pretreatment methods deploying microbes bring second-gen biofuels from oilcane closer to commercialization

In collaboration with other Bioenergy Research Centers (BRCs), researchers at the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI) are developing industrially feasible techniques for second-generation biofuel production from oilcane, an oil-rich variety of sugarcane, to help meet our growing societal demand for fuels.

In a traditional biorefinery, sugarcane is used as a feedstock to produce bioethanol fuel. These are “first-generation” biofuels – that is, fuels produced from types of biomass that are often used for food and feed. Sugarcane stalks are crushed to extract their juice, and that juice goes on to be processed into fuel. Meanwhile, the dry fibrous material that remains after crushing, a form of lignocellulose, is burned.

However, lignocellulose can also be used to produce “second-generation” biofuels – fuels that come from non-food biomass. Lignocellulose-derived fuels are particularly enticing because they do not compete with food and are suitable for large-scale production of biofuels and bioproducts, as they are widely available in the form of agricultural crop residues.

Working with lignocellulose is difficult, however. The recalcitrant structure of these materials restricts the hydrolysis of cellulose and hemicellulose to release sugars, which is necessary to produce biofuels. To access these sugars for bioprocessing, the lignocellulose must be pretreated. While there have been many advancements in converting lignocellulose into second-generation bioethanol, this process has not been widely commercialized.

Conversion pipeline

In a new inter-BRC collaboration, published in Sustainable Energy & Fuels, researchers from CABBI, the Joint BioEnergy Institute (JBEI), and the Great Lakes Bioenergy Research Center (GLBRC) investigated and compared the effects of different pretreatment methods on the oilcane lignocellulose conversion pipeline in terms of lipid recovery, sugar yield, and ethanol yield. Few prior studies have compared the viability of these pretreatment techniques, and none have been performed using oilcane.

“We are evaluating the processing of CABBI crops at an industrially relevant scale, which will help commercialize biofuel and bioproducts production from these new crops,” said Vijay Singh, CABBI team lead on the study, CABBI’s Deputy Director for Science & Technology, Distinguished and Founder Professor of Agricultural and Biological Engineering (ABE), and Executive Director of the Integrated Bioprocessing Research Laboratory (IBRL) at Illinois.

Hydrothermal pretreatment

As part of the study, CABBI researchers demonstrated the industrial viability of a hydrothermal pretreatment method, in which hot water or saturated steam is used to deconstruct the dry plant matter and prepare it for bioprocessing.

This hydrothermal pretreatment technique only requires hot water, enzymes, urea, and engineered microbes to convert lignocellulosic feedstock into bioethanol, which could make it ideal for commercialization in the future.

In addition to CABBI’s work on hydrothermal pretreatment, ammonia pretreatment was investigated by GLBRC researchers, and ionic liquid pretreatment was studied by researchers at JBEI. All the pretreatment techniques that were tested were found to be industrially viable.

“Achieving commercially viable ethanol titers from ammonia, hydrothermal, and ionic liquid-based pretreatment techniques without post-pretreatment wash and detoxification steps has excellent potential for a second-generation bioethanol refinery,” said Narendra Naik Deshavath, lead author on the study and CABBI postdoc in Singh’s lab.

Efficient and economical

The utilization of agricultural feedstock constituents, such as lignocellulose from oilcane, for conversion into biofuels has great potential to support the U.S. economy. The pretreatment techniques CABBI, JBEI, and GLBRC explored in this study allow for highly efficient and economical production of fuels at a commercial scale, which can help meet our transportation needs while reducing dependence on foreign oil.

Other CABBI co-authors on this study include Mounika Durga Nenavath and William Woodruff from the University of Illinois; Baskaran Kannan and Fredy Altpeter from the University of Florida; and Hui Liu and John Shanklin from Brookhaven National Laboratory.

JBEI co-authors on this study include Venkataramana R. Pidatala, Paul Wolski, and Alberto Rodriguez.

GLBRC co-authors on this study include Dan Xie, Kallysa Taylor, Yaoping Zhang, and Trey K. Sato.