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Lactic acid production from recycled paper sludge: Process intensification by running fed-batch into a membrane-recycle bioreactor
- Marques, S., Matos, C.T., Gírio, F.M., Roseiro, J.C., Santos, J.A.L.
- Biochemical engineering journal 2017 v.120 pp. 63-72
- Lactobacillus rhamnosus, bioreactors, biorefining, cost effectiveness, enzymes, feedstocks, fermentation, fermenters, filtration, lactic acid, lignocellulose, models, pulp and paper sludge, recycled paper, saccharification
- Production of lactic acid from recycled paper sludge by simultaneous saccharification and fermentation (SSF) has previously been implemented under a pulsed fed-batch mode. However, lactic acid concentrations above 58gL⁻¹ inhibit cultivation of the Lactobacillus rhamnosus strain used. Thereby, the present work targeted process intensification by running it into a membrane-recycle bioreactor, providing product removal together with reuse of enzymes and bacterial cells.A shear-enhanced flat sheet cross-flow filtration system was built, working properly with the high-solids concentration suspension. Based on product inhibition and solids concentration constraints, a model was proposed for operation of the membrane-recycle bioreactor. SSF should be run in batch mode into the fermentor for 48h, and then switch-on recirculation through the filtration module, with pulsed fed-batch addition of recycled paper sludge.This innovative approach can be applied to improve other SSF processes dealing with high-solids concentrations, towards cost-effective lignocellulosic feedstock biorefineries.