Simultaneous Saccharification and Fermentation of Lignocellulosics with an Acetogenic Co-culture

linenumbers Simultaneous saccharification and fermentation (SSF) of lignocellulosic substrates is often constrained by the need to reconcile the operating conditions required for enzymatic hydrolysis with those necessary for microbial growth. In addition, bioprocesses using lignocellulosic feedstocks are frequently limited by incomplete utilisation of mixed saccharides. Acetogens represent a promising alternative to traditional fermentative hosts because they metabolise a broad range of saccharides and can incorporate \ce{CO2} that is typically released as waste in conventional bioprocesses, yet their application in integrated SSF systems remains unexplored. Therefore, this study presents a framework for such an integrated approach by combining saccharification with Cellic ^{textregistered} CTec3 HS and fermentation by an acetogenic co-culture grown on pre-treated paper and cardboard waste. The pH–temperature activity profile of the enzyme mixture is mapped and compared with the physiological tolerances of Blautia schinkii and Clostridium ljungdahlii , identifying pH 6.0 and 37\,\textdegree C as conditions compatible with both enzymatic hydrolysis and acetogenic growth. Under these conditions, a 3.6\,L bioreactor trial is used to demonstrate simultaneous saccharification and fermentation of all major monosaccharides present in the feedstock. These results provide the first demonstration of integrated SSF using multiple acetogenic microorganisms and establish a foundation for developing carbon conversion efficient lignocellulosic bioprocesses.