Injection of air into the headspace improves fermentation of phosphoric acid pretreated sugarcane bagasse by Escherichia coli MM170

• Published in: Bioresource technology 2011-07, Vol.102 (13), p.6959-6965
• Main Authors: Nieves, I.U., Geddes, C.C., Mullinnix, M.T., Hoffman, R.W., Tong, Z., Castro, E., Shanmugam, K.T., Ingram, L.O.
• Format: Article
• Language: English
• Subjects: Air; Biological and medical sciences; Bioreactors - microbiology; Biotechnology; Biotechnology - instrumentation; Biotechnology - methods; Carbohydrates - chemistry; Cellulose - chemistry; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - metabolism; Fermentation - drug effects; Food industries; Fundamental and applied biological sciences. Psychology; Hydrolysis; L+SScF; Lignocellulose; Methods. Procedures. Technologies; Microaeration; Microbial engineering. Fermentation and microbial culture technology; Phosphoric Acids - pharmacology; Saccharum - chemistry; SScF; SSF; Steam; Sulfites; Use and upgrading of agricultural and food by-products. Biotechnology
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2011.04.036

► We have studied the effect of microaeration during the fermentation of sugarcane bagasse hydrolysates and unseparated slurries. ► Injecting air into the headspace increased fermentation performance by improving xylose utilization. ► Scale-up to 80 L of the L+SScF process was successful, resulting in ethanol yields of 0.25–0.27 g/g bagasse dry weight for two separate runs. Microaeration (injecting air into the headspace) improved the fermentation of hemicellulose hydrolysates obtained from the phosphoric acid pretreatment of sugarcane bagasse at 170 °C for 10 min. In addition, with 10% slurries of phosphoric acid pretreated bagasse (180 °C, 10 min), air injection into the headspace promoted xylose utilization and increased ethanol yields from 0.16 to 0.20 g ethanol/g bagasse dry weight using a liquefaction plus simultaneous saccharification and co-fermentation process (L+SScF). This process was scaled up to 80 L using slurries of acid pretreated bagasse (96 h incubation; 0.6 L of air/min into the headspace) with ethanol yields of 312–347 L (82–92 gal) per tonne (dry matter), corresponding to 0.25 and 0.27 g/g bagasse (dry weight). Injection of small amounts of air into the headspace may provide a convenient alternative to subsurface sparging that avoids problems of foaming, sparger hygiene, flotation of particulates, and phase separation.