The Improvement of Bioethanol Production by Pentose-Fermenting Yeasts Isolated from Herbal Preparations, the Gut of Dung Beetles, and Marula Wine

Table 6

Fermentation parameters of the adapted and parental yeast strains from M. caribbica Mu 2.2f with D-xylose, L-arabinose, or a mixture of the pentose sugars at 35°C with or without acetic acid.

Fermentation parameters	Absence of acetic acid						3 g/L acetic acid
	Adapted			Parental			Adapted
	D-xylose	L-arabinose	Mixture	D-xylose	L-arabinose	Mixture	D-xylose	L-arabinose
Maximum ethanol (g/L)	1.7 ± 0.5^a	3.0 ± 0.4^c	1.9 ± 0.2^b	1.5 ± 0.7^a	1.0 ± 0.11^a	1.8 ± 0.5^b	0.8 ± 0.1^b	3.6 ± 0.1^b
Ethanol yield (g/g)	0.042	0.148	0.059	0.044	0.076	0.052	0.040	0.181
Maximum arabitol (g/L)	—	16.8 ± 1.4^d	4.7 ± 3.1^d	—	7.4 ± 0.14^c	2.2 ± 0.1^b	—	20.2 ± 1.5^e
Xylitol (g/L)	2.8 ± 0.4^b	—	4.6 ± 1.6^e	8.5 ± 0.4^b	—	6.5 ± 1.3^d	3.8 ± 0.7^b	—
Arabitol yield (g/g)	—	0.494	0.347	—	0.325	0.381	—	0.657
Xylitol yield (g/g)	0.06	—	0.084	0.20	—	0.150	0.172	—
Ethanol productivity (g/L/h)	0.071	0.062	0.053	0.063	0.043	0.040	0.020	0.100

Ethanol and L-arabitol yields are reported at maximum ethanol or L-arabitol concentrations. a: after 24 hours of fermentation; b: after 36 hours of fermentation; c: after 48 hours of fermentation; d: after 72 hours of fermentation; e: after 96 hours of fermentation.