Bioethanol Production from Brewers Spent Grains Using a Fungal Consolidated Bioprocessing (CBP) Approach

Area of Science:

• Biotechnology
• Biochemical Engineering
• Sustainable Energy

Background:

• Brewers spent grains (BSG) are a significant byproduct of the brewing industry.
• Developing sustainable methods for BSG valorization is crucial for a circular economy.
• Consolidated bioprocessing (CBP) offers a promising approach for simultaneous biomass degradation and fermentation.

Purpose of the Study:

• To investigate the production of bioethanol from BSG using CBP.
• To identify optimal fungal and yeast pairings for efficient ethanol yield.
• To analyze the enzymatic activity during biomass deconstruction.

Main Methods:

• Utilized consolidated bioprocessing (CBP) with various fungal and yeast species pairings.
• Employed Aspergillus oryzae and Saccharomyces cerevisiae (NCYC479) in a sake fermentation system.
• Conducted quantitative reverse transcription PCR (QRT-PCR) to analyze carbohydrate-active enzyme (CAZy) gene expression.

Main Results:

• The sake fermentation system (A. oryzae and S. cerevisiae NCYC479) achieved the highest ethanol concentration (37 g/L within 10 days).
• One ton of dry BSG yielded 94 kg of ethanol, requiring 36 hL of water.
• QRT-PCR confirmed sequential deconstruction of hemicellulose followed by cellulose by A. oryzae.

Conclusions:

• The sake fermentation system demonstrates high potential for efficient bioethanol production from BSG via CBP.
• CBP offers a low-energy and low-water input process, despite lower productivity rates.
• Further optimization of the CBP approach is warranted for industrial application.