A strain of Saccharomyces cerevisiaeevolved for fermentation of lignocellulosic biomass displays improved growth and fermentative ability in high solids concentrations and in the presence of inhibitory compounds

Table 3 Comparison of simultaneous saccharification and fermentation methods using SO₂ pretreatment of softwoods with Saccharomyces cerevisiae strains

Yeast strain^a	Wood type	Pretreatment^b			Solids, % dry weight/volume	Inoc, g/L	Cellulase, FPU/gram dry weight	Max EtOH, g/L	Time to maximum EtOH production, hours	% TM	Reference
		SO₂ conc.	Reaction temp, °C	Duration, min
Tembec 1	Lodgepole pine	4.0	200	5	5% (washed)	5	40 FPU/g cellulase, 20 CU/g cellobiase	17.0	24	68^c	Ewanick et al. [36] (note: 6 hours enzyme preincubation)
Tembec 1	Douglas fir	4.5	195	4.5^d	40 mL, WSF	5	No enzymes added	13.8	24	87^e	Keating et al. [37]
Y-1528	Douglas fir							14.7	24	92^f
Baker's yeast	Spruce	2.5	215	5	8%	5	32 FPU/g cellulase, 28 IU/g cellobiase	Not stated	72	60^f	Alkasrawi et al. [25]
Baker's yeast^g									72	92^f
TMB 3000									48	89^f
Baker's yeast	Spruce	3.0	215	5	5%	5	15 FPU/g cellulose, 23 CU/g cellobiase	Not stated	24	49^f	Söderström et al. [35]
Baker's yeast	Spruce	3.0	210	5	12% WIS	5	15 FPU/g cellulose, 23 CU/g cellobiase	20.0 (graph)	72	37^f	Hoyer et al. [38]
XR122N	Pine	3.3	215	5	10%	4	15 FPU/g cellulose, 60 CU cellobiase	28.7	48	98^c	This study
XR122N	Pine	3.3	215	5	12%	4	15 FPU/g cellulose, 60 CU cellobiase	23.6	48	76^c	This study

Abbreviations: FPU, filter paper unit; Inoc, inoculation; CU, cellobiase unit; temp, temperature; WIS, water-insoluble solids; WSF, water-soluble fraction.
^aSaccharomyces.
^bAll biomass was pretreated with SO2 in a single step and was not delignified before pretreatment or fermentation.
^cTheoretical yield based on cellulose and hemicellulose content derived from gravimetric and analytical analyses of pretreated material.
^dSteam explosion output was diluted to 15% w/w and filtered, and the pH altered to 6.0. Suspended solids not filtered out.
^eTheoretical yield was based on the content of glucose and mannose in the pretreated material.
^fTheoretical yield was based on the content of glucose and mannose in the liquid and of glucan in the solid material.
^gIn hydrolysate.

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