Production of a generic microbial feedstock for lignocellulose biorefineries through sequential bioprocessing

Highlights

• Sugarcane bagasse and soybean hulls make excellent solid state co-substrates.

• Fungal pre-treatment deconstructs ligno-cellulosic material and produces enzymes.

• Simultaneous in-situ enzyme hydrolysis and fungal autolysis produce nutrient medium.

• Ethanol from bagasse is possible without the need for external enzymes or chemicals.

Abstract

Lignocellulosic materials, mostly from agricultural and forestry residues, provide a potential renewable resource for sustainable biorefineries. Reducing sugars can be produced only after a pre-treatment stage, which normally involves chemicals but can be biological. In this case, two steps are usually necessary: solid-state cultivation of fungi for deconstruction, followed by enzymatic hydrolysis using cellulolytic enzymes. In this research, the utilisation of solid-state bioprocessing using the fungus Trichoderma longibrachiatum was implemented as a simultaneous microbial pretreatment and in-situ enzyme production method for fungal autolysis and further enzyme hydrolysis of fermented solids. Suspending the fermented solids in water at 50 °C led to the highest hydrolysis yields of 226 mg/g reducing sugar and 7.7 mg/g free amino nitrogen (FAN). The resultant feedstock was shown to be suitable for the production of various products including ethanol.