Identification of the major fermentation inhibitors of recombinant 2G yeasts in diverse lignocellulose hydrolysates

Table 2 Composition of the lignocellulose hydrolysates used in this study and the level of spiked inhibitors

Hydrolysate Component	Bagasse BH 31B (% w/v)	Bagasse BH 18 (% w/v)	Corn cobs CCH 31A (% w/v)	Corn cobs CCH 22 (% w/v)	Spruce SH 1 (% w/v)	Inhibitor Concentration range from literature (% w/v)	Inhibitor concentrations added to each hydrolysate (% w/v)
Glucose	6.12	6.20	6.88	6.50	4.2	N.A	N.A
Xylose	3.92	4.30	5.66	4.00	1.3	N.A	N.A
Arabinose	0.20	0.27	0.47	0.40	0.32	N.A	N.A
Acetic Acid	0.53	0.43	0.63	0.60	0.70	0.10–1.10	0.03, 0.06, 0.10, 0.30, 0.60, 0.80
Levulinic Acid	0.01	0.00	0.00	0.00	0.17	0.00–0.32	0.03, 0.06, 0.10, 0.30, 0.60
Formic Acid	0.06	0.03	0.03	0.03	0.03	0.00–0.68	0.03, 0.06, 0.10, 0.30, 0.60
Furfural	0.03	0.03	0.04	0.02	0.27	0.02–0.35 *	0.03, 0.06, 0.10, 0.30, 0.60
HMF	0.01	0.02	0.01	0.02	0.53	0.01–0.59**	0.03, 0.06, 0.10, 0.30, 0.60
4-hydroxy benzoic acid	N.D	N.D	N.D	N.D	N.D	0.0000–0.0011	0.0001, 0.0003, 0.0010
4-hydroxy benzaldehyde	N.D	N.D	N.D	N.D	N.D	0.0000–0.0110	0.0003, 0.0010, 0.0030
Vanillin	N.D	N.D	N.D	N.D	N.D	0.000–0.041	0.003, 0.010, 0.030

The concentration of sugars and inhibitors present in the hydrolysates, as well as the inhibitor concentrations spiked, are indicated. The inhibitor concentration range described in the literature for weak acids and furan aldehydes is derived from the data collected in Table 1 and for the phenolic compounds based on other literature references [40, 57, 58]
NA not applicable, ND not determined, BH bagasse hydrolysate, CCH corn cob hydrolysate, SH spruce hydrolysate
*Concentrations of furfural present in lignocellulose hydrolysates were found to be up to 0.35% (w/v) (Table 1), with exception of corn stover hydrolysates in two studies (up to 0.85% (w/v) [35] and 1.10% (w/v) furfural [55])
**HMF concentrations present in different lignocellulose hydrolysates were found to be up to 0.59% (w/v) (Table 1), with exception of hydrolysates from woody energy crops pre-treated at high temperature (at least 222 °C) (up to 0.86%, w/v, HMF). The same biomasses pre-treated at lower temperatures contained HMF concentrations below 0.59% (w/v) [34]

ISSN: 2731-3654