Sugarcane bagasse pretreatment using three imidazolium-based ionic liquids; mass balances and enzyme kinetics

Table 3 Mass balance of bulk biomass and of biomass components from three treatments with different ILs

Dry mass (mg)	Bulk biomass	Ash	Lignin (AIL + ASL)	Glucan	Xylan	Arabinan	Acetyl	HMF	Furfural
[C4mim]Cl
Untreated	1461	46	383	656	324	22	46	n/a	n/a
SF1	1318	47	344	627	270	14	39	n/a	n/a
LF1	92	n/d	0.4*	16	60	10	7	0.6	1.2
LF1 oligo				13	58	2	6
Total mass recovered	1411	47	344	636	317	24	46
[C2mim]Cl
Untreated	1346	42	353	605	299	20	42	n/a	n/a
SF1	643	39	185	343	71	4	11	n/a	n/a
LF1	446	n/d	3*	188	214	14	28	1.2	1.4
LF1 oligo				175	204	3	27
Total mass recovered	1089	39	188	516	267	20	39
[C2mim]OAc
Untreated	699	22	183	314	155	10	22	n/a	n/a
SF1	463	26	73	316	62	7	7	n/a	n/a
LF1	88	n/d	17*	1	85	5	n/d	1.1	1.8
LF1 oligo				bdl	83	5	n/d
Total mass recovered	551	26	90	316	125	12	7

Masses (average of duplicates).
Masses expressed on dry basis. Glucan is considered equal to cellulose, HMF (Hydroxymethyl furfural) is expressed as glucan equivalents and furfural as xylan equivalents, SF1: solid fraction 1, recovered from the first water addition (water:IL mass ratio = 0.5), LF1: liquid fraction 1, recovered from the first water addition (water:IL mass ratio = 0.5), LF1 oligo: oligosaccharides in LF1, n/d: not determined, n/a: not applicable, bdl: barely detectable.
The estimates of standard deviation (absolute, based on duplicate IL pretreatments, 3 df) of the recovery (and analysis) of these components (as%mass starting component) in SF1 are 2% for glucan, 2% for xylan, 3% for arabinan, 1% for acetyl and 2% for lignin (acid soluble + acid insoluble). In LF1, these estimates of standard deviation for the oligosaccharides are 1% for glucan, 2% for xylan, 18% for arabinan and 3% for acetyl and for the monosaccharides they are 0.2% for glucan, 0.2% for xylan, 15% for arabinan and 0.7% for acetyl. The unacceptably high standard deviation for arabinan is attributed to its very low concentrations in the liquid fractions. *This mass does not represent all the lignin mass in the LF1 but only the recoverable lignin mass in the sum of SF2 and SF3 precipitates.

ISSN: 2731-3654