Adaptive Evolution of Saccharomyces cerevisiae in a Continuous and Closed Circulating Fermentation (CCCF) System Coupled with PDMS Membrane Pervaporation

Abstract

As an efficient means of strain improvement, adaptive evolution is a technique with great potential. Long-term cultivation of Saccharomyces cerevisiae was performed in a polydimethylsiloxane membrane bioreactor system which was constructed by coupling the fermentation with pervaporation. A parent strain was subjected to three rounds of fermentation-screening-transfer procedure lasting 1,500 h in a continuous and closed circulating fermentation (CCCF) system, and its 600-generation descendant S33 was screened. In shaking flask culture test, the selected strain S33 from the third round showed great superiority over the parent strain in the residual broth medium, with the ethanol yield and specific ethanol productivity increasing by 34.5 and 34.7 %, respectively. In the long-term CCCF test, the fermentation performance of the descendant strain in the third round was higher than that of its parent strain in the second round. These results show the potential of this novel adaptive evolution approach in optimization of yeast strains.

Using a Novel Pervaporative Sequential-Co-immobilized Two-Sectional Bioreactor with an Ultralow Fouling–Biofouling Superhydrophobic Silicallite-1/PDMS Membrane to Enhance Bioethanol Production

“…35,36 In the pervaporation part, considerable differences were observed in the separation factor and pervaporative separation index of TSP compared to the use PDMS and zeolite/PDMS membranes in the literature. 10,13,14,16,61,64 This disagreement can be related to having simultaneous antiswelling properties, ultralow fouling−biofouling formation, and high inherent pervaporation performance of TSP (high performance in separating ethanol from the synthesis solution) compared to others. In fact, high membrane hydrophobicity (contact angle) has not been addressed in the literature.…”

“…In the literature, the performance of single cultures of S. cerevisiae to ferment single glucose media was surveyed mostly at low sugar levels in PMBR, ,,− ,,,, which are not in accordance to sugar levels in the real hydrolysate of lignocellulosic materials. , In fact, the low level of sugar and ignoring xylose provide unaffordable bioethanol production . A suspended cell was often used, and this could have led to fouling/biofouling formation. , In the pervaporation part, considerable differences were observed in the separation factor and pervaporative separation index of TSP compared to the use PDMS and zeolite/PDMS membranes in the literature. ,,,,, This disagreement can be related to having simultaneous antiswelling properties, ultralow fouling–biofouling formation, and high inherent pervaporation performance of TSP (high performance in separating ethanol from the synthesis solution) compared to others. In fact, high membrane hydrophobicity (contact angle) has not been addressed in the literature.…”

“…In these equations, x and y refer to the weight percent of molecules in the permeate and feed, respectively; subscripts i and j denote ethanol and water molecules, respectively; and m (kg), t (h), and A (m 2 ) indicate the permeate weight, permeation time, and effective surface area of the membrane, respectively. 10 x x y y ( / )/( / )…”

“…To calculate the pervaporation performance, the separation factor (α) and permeation flux ( J ) were calculated via the following equations. In these equations, x and y refer to the weight percent of molecules in the permeate and feed, respectively; subscripts i and j denote ethanol and water molecules, respectively; and m (kg), t (h), and A (m 2 ) indicate the permeate weight, permeation time, and effective surface area of the membrane, respectively α = ( x i / x j ) / ( y i / y j ) J = m / ( A × t ) …”

“…PMBRs have been mostly surveyed in simplistic conditions that are far from reality. A single carbon substrate (glucose) at a range of 67.5–150 g/L has mostly been fermented by suspended S. cerevisiae as a glucose-fermenting strain. − Limited studies have focused on fermenting glucose by immobilized S. cerevisiae in calcium alginate (CA) and hybrid CA-polyvinylalcohol (PVA) beads.…”