Ethanol production from non-detoxified hardwood spent sulfite liquor in submerged fed-batch culture using advanced yeasts

Abstract To improve process feasibility, it is essential to use hardwood spent sulfite liquor (HSSL) as the main feedstock for bioethanol production, without prior detoxification. In addition, operating at large-scale under cost-effective conditions such a small inoculum size (< 1 g/L), pH 5, using industrially acceptable nutrients, and sugar will require of harsh, concentrated HSSL streams. The potential non-detoxified ethanol production two recombinant Saccharomyces cerevisiae strains, CelluX™4 TFA7, was assessed. inhibitory effect mitigated, titer increased from 4.1 7.9 g/L when pulse fed-batch used instead batch with performing best. Both strains made xylose isomerase (XI) pathway, strain TFA7 engineered tolerance against inhibitors. By administering in pulses shake-flask cultures, could be by approximately 50–90% compared simple cultures supplemented 20%, 40%, 60% (v/v) dilutions HSSL. non-aerated, non-sterile 5-L bioreactor fermentations low cell concentration 5 corn steep (CSL) nitrogen source. comparison, undiluted fed continuously obtain final 65% supplementation, which corresponded total 70.8–80.8 g/L. Despite harsher, inexpensive conditions, reactor obtained yields 0.35–0.43 g/g, which, based on maximum theoretical yield 0.51 g/g hexoses or pentoses, corresponds efficiencies 68.6 84.3%. This illustrates an improvement highest titers reported literature advanced industrial S. strain, CelluX™4, combined strategy, offers straightforward real upscaling fermentations.