Gaseous ammonia pretreatment lowers the required energy input for fine milling-enhanced enzymatic saccharification of switchgrass

Table 4 Saccharification yields, milling energy and energy efficiency of milled switchgrass samples at different enzyme loadings

Sample 7 mg enzyme/g (glucan + xylan)	Energy input during fine milling (MJ/kg)	Monomeric + oligomeric Glucose % theor. yield	Glucose mass yield (kg/kg biomass)	Energy efficiency (glucose mass yield/energy input) (MJ/kg)	Monomeric + oligomeric Xylose % theor. yield	Xylose mass yield (kg/kg biomass)	Energy efficiency (xylose mass yield/energy input) (MJ/kg)	Energy efficiency (glucose + xylose mass yield/energy input) (MJ/kg)
Union process attritor mill, 5 min	0.958	61.75	0.2334	0.244	81.13	0.1874	0.196	0.439
Hosokowa 2ACM Air-classifier mill	1.801	55.81	0.2110	0.117	74.56	0.1722	0.0957	0.213
Fluid energy model 4 microjet, jet mill	5.40	57.06	0.2157	0.0399	75.74	0.1750	0.0461	0.0886
Kemutec 5H universal pin mill, 2 passages	ND	53.57	0.2025		74.88	0.1730
NH₃-treated unmilled	NA	49.58	0.1874		59.61	0.1377
Sample 14 mg enzyme/g (glucan + xylan)
Attritor mill	0.958	81.77	0.3091	0.323	91.81	0.2121	0.221	0.544
Air-classifier mill	1.801	70.62	0.2669	0.148	83.18	0.1921	0.1068	0.255
Jet mill	5.40	66	0.2495	0.0462	74.11	0.1712	0.0319	0.0779
Pin mill, 2 passages	ND	59.69	0.2256		73.46	0.1697
NH₃-treated unmilled	NA	57.09	0.2158		63.07	0.1457
Sample 28 mg enzyme/g (glucan + xylan)
Attritor mill	0.958	82.57	0.3121	0.326	87.36	0.2018	0.211	0.537
Air-classifier mill	1.801	79.83	0.3018	0.168	87.65	0.2025	0.112	0.280
Jet mill	5.40	76.31	0.2885	0.0534	85.23	0.1969	0.0365	0.0899
Pin mill, 2 passages	ND	72.54	0.2742		79.36	0.1833
NH₃-treated unmilled	NA	61.89	0.2339		64.21	0.1483

Saccharification yields and milling energies for milling trials on UT-4b NH₃-treated (150–160 °C, 1 h) switchgrass. Each of the samples was saccharified at a 25 % solids loading for 120 h with three different concentrations of Accellerase^® DUET at 7, 14 and 28 mg protein/g (glucan + xylan). The sugar yields are based on soluble monomer plus oligomer

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