Fig 1.
Inert supports used for cell immobilization.
From left to right: plastic Raschig rings, Tygon silicone Raschig rings, glass Raschig rings and alumina beads.
Fig 2.
Fermentation performance of K. marxianus DSM 7239, DSM 5418, DSM 5422 and DSM 70799 in concentrated synthetic medium (Li = 130 g/L).
Parameters: final ethanol concentration (Ef), ethanol yield conversion efficiency (ηE), lactose consumption (ΔL) and productivity (WE). The different letters above ethanol bars (a, b, c) indicate the existence of significant differences (p < 0.05) among strains for ethanol production. If two strains share one letter, there are no significant differences between them.
Fig 3.
Evaluation of the effect of different combinations of nutrients on alcoholic fermentation performance.
Response variables: Ethanol final concentration (Ef), ethanol yield conversion efficiency (ηE), lactose consumption (ΔL) and productivity (WE) of K. marxianus 5422 employing concentrated CWP (Li = 130 g/L). Description of nutrient preparations: A (3 g/L yeast extract, 2 g/L NH4Cl, 2 g/L KH2PO4, and 2 g/L K2HPO4), B (1 g/L MgSO4·7H2O), C (200 mg/L sodium thioglycolate). The different letters above ethanol bars (a, b, c, d, e) indicate the existence of significant differences (p < 0.05) among samples for ethanol production. If two samples share one letter, there are no significant differences between them.
Table 1.
Fermentation performance of S. cerevisiae CECT 1383, Ethanol Red, CECT 13152 and Hércules in hydrolyzed CWP (Li = 140 g/L).
Table 2.
Experimental results of ethanol concentration (Ef), ethanol yield factor (YE/L), ethanol profit factor (πE) and ethanol volumetric productivity (WE) according to a central composite design employing K. marxianus DSM 5422 for the fermentation of CWP (Li = 132.5 g/L).
Table 3.
Experimental results of ethanol concentration (Ef), ethanol yield factor (YE/L), ethanol profit factor (πE) and ethanol volumetric productivity (WE) according to a central composite design employing S. cerevisiae Ethanol Red for the fermentation of hydrolyzed CWP (Li = 132.5 g/L).
Fig 4.
Evolution of ethanol concentration during ethanol fermentation for inorganic supports [glass Raschig rings (GRR), plastic Raschig rings (PRR), tygon Raschig rings (TRR) and alumina beads (AB)] during 7 fermentation cycles (Li = 130 g/L) employing K. marxianus DSM 5422.
Asterisks indicate the existence of significant differences (p < 0.05) among supports for a given batch. If two supports share one letter (a, b or c), there are no significant differences between them.
Fig 5.
Evolution of ethanol concentration employing K. marxianus DSM 5422 on inorganic supports [glass Raschig rings (GRR) and alumina beads (AB)] during 14 fermentation cycles (Li = 130 g/L).
Asterisks indicate the existence of significant differences (p < 0.05) between supports for a given batch.
Fig 6.
Evolution of ethanol concentration employing K. marxianus DSM 5422 on inorganic supports [glass Raschig rings (GRR) and alumina beads (AB)] during 14 fermentation cycles (Li = 170 g/L).
Asterisks indicate the existence of significant differences (p < 0.05) between supports for a given batch.
Table 4.
Comparison of mean fermentation parameters for K. marxianus DSM 5422 during the 14 cycles employing CWP with lactose loads of 130 g/L and 170 g/L for glass Raschig rings (GRR) and alumina beads (AB) supports.