Process intensification through microbial strain evolution: mixed glucose-xylose fermentation in wheat straw hydrolyzates by three generations of recombinant Saccharomyces cerevisiae

Table 5 Laboratory evolution of xylose-fermenting strains of S. cerevisiae as tool for process intensification: comparison of key process parameters reported for the progenitor strain and the evolved strain, respectively

Progenitor strain - evolved strain	Fermentation condition^b	c_Sugar(g/L)^c	q_Xylose(g/g_CDW/h)	c_Ethanol(g/L)^d	Y_Ethanol(g/g_{total sugars})	μ_max(h^-1)^e	Source
Genetic background ^a	Fermentation condition^b	c_Sugar(g/L)^c	q_Xylose(g/g_CDW/h)	c_Ethanol(g/L)^d	Y_Ethanol(g/g_{total sugars})	μ_max(h^-1)^e	Source
TMB3001 -	MM	Glc: 50	0.08*	22*	0.38*	0.44^Glc	[26]
TMB3001C1	AN	Xyl: 50	0.31*	28*	0.40*	0.44^Glc
XR/XDH/XK	LCD		(3.9–fold)	(1.3–fold)	(1.1–fold)	(–)
H131-A3^SB-2 -	YE	Xyl: 40	0.26	4*	0.42	0.06^Xyl	[39]
H131-A3^CS	AN		0.94	15*	0.43	0.12^Xyl
XI/ PPP/ T	LCD		(3.6–fold)	(3.8–fold)	(–)	(2–fold)
HDY.GUF5 -	YE, Pep	Glc: 36	0.13	18*	0.23	n.a.	[23]
GS1.11-26	Semi-AN	Xyl: 37	1.10	34*	0.46	n.a.
XI/PPP	HCD		(8.5–fold)	(1.9–fold)	(1.8–fold)	(–)
BP10001 -	YE	Xyl: 50	0.37	0.9	0.30	-	This study
IBB10B05	AN		1.04	2.8	0.31	0.02^Xyl
XR/XDH/XK	LCD		(2.8–fold)	(3.1–fold)	(–)	(–)
TMB3400 -	Wheat straw hydrolyzate, YE, salts, pH 5	Glc: 7.6	0.20*	5.5	0.20	-	[34]
KE6-13i	AN	Xyl: 38	0.04*	6	0.27	-
XR/XDH/XK	HCD		(-)	(1.1–fold)	(1.4–fold)	(–)
TMB3400 -	Spruce hydrolyzate, MM, pH 5		n.a.	7.8*	0.40	0.07^Glc	[24]
KE1-17	AN	Glc: 18	n.a.	7.9*	0.43	0.08^Glc
XR/XDH/XK	LCD	Xyl: 9	(–)	(–)	(1.1–fold)	(1.14–fold)
BP10001 -	Wheat straw hydrolyzate, YE, pH 6.5		0.02	4	0.40	0.10^Glc	This study
IBB10B05	AN	Glc: 32	0.35	21	0.39	0.19^Glc
XR/XDH/XK	HCD	Xyl: 16	(17.5–fold)	(5.3–fold)	(–)	(1.9–fold)

^aStrain background: PPP, overexpression of genes from the pentose phosphate pathway; T, overexpression of the HXT7 transporter; XDH, xylitol dehydrogenase; XI, xylose isomerase; XK, xylulose kinase; XR, xylose reductase. ^bAN, anaerobic; HCD, high cell density (start OD₆₀₀ of fermentation ≥1); LCD, low cell density (start OD₆₀₀ of fermentation ≤0.5); MM, mineral medium; Pep, peptone; YE, yeast extract. ^cInitial sugar concentration of the substrate. ^dEthanol produced within the first 50 h of fermentation or earlier, when sugars were depleted before. ^eMaximal growth rate on glucose (Glc) or xylose (Xyl). n.a., not analyzed; in parenthesis, improvement calculated from the evolved strain as compared to the progenitor strain; *Data are derived from the time courses given in the respective publications.

ISSN: 2731-3654