Simultaneous saccharification and ethanol fermentation at high corn stover solids loading in a helical stirring bioreactor.

The higher ethanol titer inevitably requires higher solids loading during the simultaneous enzymatic saccharification and fermentation (SSF) using lignocellulose as the feedstock. The mixing between the solid lignocellulose and the liquid enzyme is crucially important. In this study, a bioreactor with a novel helical impeller was designed and applied to the SSF operation of the steam explosion pretreated corn stover under different solids loadings and different enzyme dosages. The performances using the helical impeller and the common Rushton impeller were compared and analyzed by measuring rheological properties and the mixing energy consumption. The results showed that the new designed stirring system had better performances in the saccharification yield, ethanol titer, and energy cost than those of the Rushton impeller stirring. The mixing energy consumption under different solids loadings and enzyme dosages during SSF operation were analyzed and compared to the thermal energy in the ethanol produced. A balance for achieving the optimal energy cost between the increased mixing energy cost and the reduced distillation energy cost at the high solids loading should be made. The potentials of the new bioreactor were tested under various SSF conditions for obtaining optimal ethanol yield and titer.

Simultaneous saccharification and microbial lipid fermentation of corn stover by oleaginous yeast Trichosporon cutaneum.

Simultaneous saccharification and fermentation (SSF) is the most commonly practiced operation in lignocellulose bioconversion to avoid the sugar product inhibition to cellulase enzymes. In this study, for the first time SSF was tested on microbial lipid fermentation using the diluted acid pretreated and biodetoxified corn stover. The results show that SSF was effective than the separate hydrolysis and fermentation (SHF) on lipid accumulation of Trichosporon cutaneum CX1 cells in both the small scale (5L) and the enlarged scale (50 L) bioreactors. The solutions for the oxygen transfer and the lipid extraction in SSF practically worked well. The process parameters were optimized and the lipid yield obtained were 3.03 g/L in the 5L, and 3.23 g/L in the 50 L, respectively. The result also shows that the cellulase enzyme could be partially recycled in the SSF. The study provided a practical and efficient way for microbial lipid production from lignocellulose material.

[Process strategy for ethanol production from lignocellulose feedstock under extremely low water usage and high solids loading conditions].

The massive water and steam are consumed in the production of cellulose ethanol, which correspondingly results in the significant increase of energy cost, waster water discharge and production cost as well. In this study, the process strategy under extremely low water usage and high solids loading of corn stover was investigated experimentally and computationally. The novel pretreatment technology with zero waste water discharge was developed; in which a unique biodetoxification method using a kerosene fungus strain Amorphotheca resinae ZN1 to degrade the lignocellulose derived inhibitors was applied. With high solids loading of pretreated corn stover, high ethanol titer was achieved in the simultaneous saccharification and fermentation process, and the scale-up principles were studied. Furthermore, the flowsheet simulation of the whole process was carried out with the Aspen plus based physical database, and the integrated process developed was tested in the biorefinery mini-plant. Finally, the core technologies were applied in the cellulose ethanol demonstration plant, which paved a way for the establishment of an energy saving and environment friendly technology of lignocellulose biotransformation with industry application potential.