Sulphite addition during steam pretreatment enhanced both enzyme-mediated cellulose hydrolysis and ethanol production

Bioresources and Bioprocessing

Table 2 The sugar, lignin, acid group and potential inhibitor content as well as fiber length/width and cellulose hydrolysis of water soluble/insoluble fractions of SO₂-catalyzed acid bisulphite steam-pretreated substrates

Samples	Water insoluble^a										Water soluble^b						Water-soluble inhibitors				pH	Enzymatic hydrolysis^c
Samples	Ara (%)	Gal (%)	Glu (%)	Xyl (%)	Man (%)	AISL (%)	Lignin removal (%)	Acid groups (μ mol/g substrates)	Fiber length (mm)	Fiber width (um)	Glu M (g/L)	Glu O (g/L)	Xyl M (g/L)	Xyl O (g/L)	Man M (g/L)	Man O (g/L)	Acetic acid (g/L)	Furfural (g/L)	HMF (g/L)	Total phenolics (g/L)	pH	Glucan hydrolysis yield (%)
4% SO₂ 200 ℃ 5 min	0	0.1	48.0	0.1	0.3	49.0	0.1	15.0	1.3	31.9	28.2	7.1	11.2	2.2	17.7	8.9	8.2	3.2	1.6	4.7	1.7	54.5
8% NaHSO₃ + 2%H₂SO₄, 210 ℃ 10 min	0.1	0.2	62.1	1.4	2.2	32.5	33.0	88.0	0.4	27.3	0.6	3.3	1.5	0.6	2.5	4.8	0.9	0.3	0.2	7.6	3.6	58.1

The sugars, pH, and fermentation inhibitors present in the water-soluble fraction of acid bisulphite steam-pretreated lodgepole pine substrates based on 25% solid loading whole slurry
Enzymatic hydrolysis yields of single-stage acid bisulphite steam-pretreated lodgepole pine whole slurries. The hydrolysis was performed at a 25% solid loading for 48 h using a cellulase enzyme loading of 40 mg protein/g cellulose
^aWater insoluble: Ara—arabinan, Gal—galactan, Glu—glucan, Xyl—xylan, Man—mannan, AISL—acid-insoluble lignin
^bWater soluble: Glu—glucose, Xyl—xylose, Man—mannose, M—monomer, O—oligomer
^cEnzymatic hydrolysis was conducted at 25% solids loading with a Ctec-3 enzyme loading of 40 mg protein/g glucan for 48 h