Ethanol production potential from AFEX™ and steam-exploded sugarcane residues for sugarcane biorefineries

Table 2 Summary of fermentation parameters of steam-exploded and AFEX™-treated bagasse and cane leaf matter

Parameter	AFEX™—bagasse	StEx—bagasse—unwashed solids	StEx—bagasse—washed solids	StEx—bagasse—whole slurry	StEx—bagasse—C₅-liquor	AFEX™—CLM	StEx—CLM—unwashed solids	StEx—CLM—washed solids	StEx—CLM—whole slurry	StEx—CLM—C₅-liquor
Initial glucose conc. (g L⁻¹)	59.03	83.89	97.56	69.67	2.89	58.45	96.27	101.49	68.30	2.10
Initial xylose conc. (g L⁻¹)	37.01	11.22	5.60	26.09	21.19	35.15	12.38	7.70	27.95	26.18
Glucose consumption (%)	100	100	100	98	100	100	100	100	99	100
Xylose consumption (%)	96	90	95	37	29	95	97	96	41	61
µ_max (h⁻¹)^a	0.31	0.24	0.27	0.05	0.013	0.3	0.25	0.32	0.055	0.015
Y _x/s (g CDW/g sugar)^b	0.05	0.04	0.04	0.03	0.02	0.05	0.04	0.04	0.03	0.01
Metabolic yield (%)^c	92	91	89	87	69	89	89	90	87	71
Y_p/s (g EtOH/g sugar)^d	0.46	0.45	0.45	0.36	0.13	0.44	0.45	0.46	0.36	0.23
EtOH conc. (g L⁻¹)	44.17	43.48	46.75	34.62	3.18	41.70	49.24	50.21	35.07	6.48
EtOH yield (kg/100 kg DM)^e	25.60	16.54	16.84	16.23	1.69	24.90	15.98	16.58	16.67	3.75

All hydrolysates were supplemented with 0.25% (w/w) corn steep liquor prior to fermentation. The C₅-liquor/s were acid hydrolysed to convert oligosaccharides to their monomeric counterparts prior to fermentation
Data represent the averages of independent duplicate fermentation cultivations. All standard errors were less than 5%
^aMaximum specific growth rate: maximum growth rate calculated in the exponential growth phase
^bCell biomass yield: gram of cell dry weight per gram of sugar (glucose + xylose) consumed during fermentation
^cMetabolic yield: gram of ethanol produced per gram of sugar (glucose + xylose) consumed during fermentation
^dEthanol yield: gram ethanol produced per gram of sugar at the beginning of fermentation
^eEthanol yield per 100 kg of untreated dry material

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