Batch and fed-batch simultaneous saccharification and fermentation of primary sludge from pulp and paper mills.
Primary sludge from a Portuguese pulp and paper mill, containing 60% of carbohydrates, and unbleached pulp (as reference material), with 93% of carbohydrates, were used to produce ethanol by simultaneous saccharification and fermentation (SSF). SSF was performed in batch or fed-batch conditions without the need of a pretreatment. Cellic®CTec2 was the cellulolytic enzymatic complex used and Saccharomyces cerevisiae (baker's yeast or ATCC 26602 strain) or the thermotolerant yeast Kluyveromyces marxianus NCYC 1426 were employed. Primary sludge was successfully converted to ethanol and the best results in SSF efficiency were obtained with S. cerevisiae. An ethanol concentration of 22.7 g L-1was produced using a content of 50 g L-1of carbohydrates from primary sludge, in batch conditions, with a global conversion yield of 81% and a production rate of 0.94 g L-1h-1. Fed-batch operation enabled higher solids content (total carbohydrate concentration of 200 g L-1, equivalent to a consistency of 33%) and a reduction of three-quarters of cellulolytic enzyme load, leading to an ethanol concentration of 40.7 g L-1, although with lower yield and productivity. Xylitol with a concentration up to 7 g L-1was also identified as by-product in the primary sludge bioconversion process.
a CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology , University of Coimbra , Coimbra , Portugal.
Cátia Vanessa Teixeira
CVT
Mendes
a CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology , University of Coimbra , Coimbra , Portugal.
Jorge Manuel Dos Santos
JMDS
Rocha
a CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology , University of Coimbra , Coimbra , Portugal.
Fabrícia Farias
FF
de Menezes
a CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology , University of Coimbra , Coimbra , Portugal.
Maria da Graça Videira Sousa
MDGVS
Carvalho
D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D007220:Industrial Waste; D007716:Kluyveromyces / Q000378:metabolism; D010209:Paper; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D018505:Waste Management / Q000379:methods*; D014993:Xylitol / Q000378:metabolism
D007220:Industrial Waste; D000431:Ethanol; D014993:Xylitol
Batch; ethanol; fed-batch; primary sludge; simultaneous saccharification fermentation