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Scale-up of multi feed fed-batch simultaneous saccharification and co-fermentation of pretreated wheat straw to ethanol

Johan Westman (Institutionen för biologi och bioteknik, Industriell bioteknik) ; Ruifei Wang (Institutionen för biologi och bioteknik, Industriell bioteknik) ; Pornkamol Unrean (Institutionen för biologi och bioteknik, Industriell bioteknik) ; Lisbeth Olsson (Institutionen för biologi och bioteknik, Industriell bioteknik) ; Carl Johan Franzén (Institutionen för biologi och bioteknik, Industriell bioteknik)
37th Symposium on Biotechnology for Fuels and Chemicals (2015)
[Konferensbidrag, poster]

A major remaining issue with second-generation bioethanol production is the difficulty of reaching high enough titers to facilitate an overall economical process. Utilization of approximately 20% pretreated insoluble lignocellulosic material in the process is necessary to reach an often mentioned ethanol concentration of 4-5% (w/w). The viscosity at this solids concentration becomes higher than what is easily attainable in most reactor set-ups. We have designed a fed-batch simultaneous saccharification and co-fermentation (SSCF) process for ethanol production from pretreated wheat straw up to 21% water insoluble solids in a stirred tank reactor. In addition to feeding of solids at different time points, feeding of fresh cells at different time points was found to be beneficial for the process. The fed cells were adapted to the toxic environment by pre-cultivation in the liquid fraction from the pretreatment. Enzyme addition at different time points did however not improve the process, compared to addition of the same total amount in the beginning of the fed-batch. The effectiveness of the optimized process has been proven at demonstration scale in a 10 m3 SSCF reactor, reaching ethanol concentrations of 5% (w/w). A further increase was hindered by the toxicity of the medium, lowering the cells’ fermentation capacity. We have previously shown that strong flocculation can increase the ability of yeast to ferment toxic lignocellulose hydrolysates [1]. We therefore created strongly flocculating xylose fermenting Saccharomyces cerevisiae strains and are currently investigating these in the SSCF process. [1] Westman et al. Appl Environ Microbiol, 2014.

Nyckelord: Lignocellulosic ethanol, Fed-batch SSCF model, Scale-up, Flocculation



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Denna post skapades 2015-09-30. Senast ändrad 2015-09-30.
CPL Pubid: 223456