Converting the lignocellulose in biomass into fermentable sugars and ultimately biochemicals with the help of enzymes requires first breaking down the tough lignocellulosic structure. The technology already exists, but the inhibitors generated by the process reduce the effectiveness of the enzymes. Inhibitors are chemical compounds that prevent or hinder enzyme activity. Enzymes that are more resistant to inhibitors could help to lower enzyme costs and increase the sugar yield.

Specifically, the IndZyme project aims at the discovery of inhibitor-tolerant cellobiohydrolases (CBHs) and lytic polysaccharide monooxygenases (LPMOs). CBHs are the major activities in the hydrolysis of cellulose, whereas LPMOs have recently been shown to significantly boost the hydrolysis.

The unique culture collection of IndZyme partner VINSTROM (India) containing fungi isolated from fire-prone forests will be used as a source for enzyme screening. The fungi are adapted to growing on burned wood where similar inhibitors are present as in pretreated lignocellulose.

During the project, these microbial cultures will be screened for new, more inhibitor-resistant cellulase enzymes as well as LPMO enzymes, whose activity may even be boosted by inhibitor chemicals.

The next step will be studying the efficiency of these new enzymes in breaking down agricultural waste, such as straw, into fermentable sugars. These new enzymes will be compared against the Trichoderma reesei enzymes, which are widely used in industrial applications, and enzyme mixtures. The project will involve developing new enzyme screening methods and producing new information about compounds that inhibit or promote enzyme activity.

Special attention will be given to lignin-based phenolic compounds, which are released at high temperatures during the pretreatment of lignocellulosic materials. These compounds are strong inhibitors of cellulase enzymes but can act as electron donors and therefore increase LPMO enzyme activity.

Lignocellulosic agricultural waste is among the most common renewable biomass resources. In Europe, wheat straw is one of the most abundant agricultural waste products. India has ample stocks of bagasse, the fibrous matter that remains after sugar cane stalks are crushed to produce sugar, but it is currently disposed of by incineration, causing considerable local emissions.

The IndZyme project consortium comprises VTT (Finland), VINSTROM (India), RWTH (Germany) and the University of Tartu (Estonia). VINSTROM will screen the microbial cultures, after which VTT will analyse them for the enzymes they produce. RWTH will fraction the inhibitor compounds generated by biomass processing, after which VTT and the University of Tartu will characterise the enzymes and study their interactions with inhibitors. The project is part of the EU’s Inno Indigo program, which aims to increase research cooperation between Europe and India.

The three-year project is coordinated by VTT, and its total budget is approximately €1 million (US$1.2 million). VTT and the Academy of Finland have allocated a total of €400,000 towards the project (VTT 70%, Academy of Finland 30%). The project coordinator is VTT’s Research Professor Kristiina Kruus.