Abstract
The yeast cells of Kluyveromyces marxianus immobilized on Nypa fruticans leaf sheath pieces was tested for acetic acid tolerance during ethanol fermentation. Control sample with the free yeast cells were also performed under the same conditions. When the acetic acid content in the medium varied from 0 to 8g/L, the cell growth rate of the immobilized and free yeast decreased by 8.3 to 10.3 time, respectively. In addition, increase in acetic acid content from 0 to 8g/L reduced ethanol formation rate of the immobilized and free yeast by 4.1 to 6.8 times, respectively. The immobilized yeast always demonstrated faster sugar assimilation and higher final ethanol concentration than the free yeast. Under acetic acid stress, the fixed yeast exhibited less change in unsaturated degree of fatty acids in cellular membrane than the free yeast. Application of immobilized yeast was therefore potential for improvement in ethanol fermentation from lignocellulosic material.
Highlights
Lignocellulosic biomass such as wood, grass and agriculture residue have been reported as an attractive material for bioethanol production due to their abundance in nature and low cost [1, 2]
In the production of bioethanol, pretreatment of lignocellulosic biomass is essential since this process can remove lignin and reduce the crystallinity of cellulose
The objective of this study was to evaluate the effect of acetic acid on the growth, glucose assimilation and ethanol fermentation by the immobilized yeast K. marxianus on Nypa fruticans leaf sheath pieces
Summary
Lignocellulosic biomass such as wood, grass and agriculture residue have been reported as an attractive material for bioethanol production due to their abundance in nature and low cost [1, 2]. In the production of bioethanol, pretreatment of lignocellulosic biomass is essential since this process can remove lignin and reduce the crystallinity of cellulose. There have been many pretreatment methods, among which weak acidic hydrolysis has been widely used because of low cost and high efficiency for lignin and hemicellulose removal [3, 4]. Diluted acid pretreatment generates toxic compounds, such as weak acids, furans and phenolics, which strongly inhibit the biological reactions of yeast during the ethanol fermentation [5]. Leaf sheath pieces was proved as appropriate support due to its high porosity for cell adsorption [9]
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