Performance of microorganisms in spent sulfite liquor and enzymatic hydrolysate of steam-pretreatedSalix (original) (raw)
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Biomass Conversion and Biorefinery
To improve process feasibility, it is essential to use hardwood spent sulfite liquor (HSSL) as the main feedstock for bioethanol production, without prior detoxification. In addition, operating at large-scale under cost-effective conditions such as a small inoculum size (< 1 g/L), pH 5, using industrially acceptable nutrients, and without sugar addition, will require the use of harsh, concentrated HSSL streams. The potential of non-detoxified HSSL as a feedstock for ethanol production using two recombinant Saccharomyces cerevisiae strains, CelluX™4 and TFA7, was assessed. The inhibitory effect of non-detoxified HSSL was mitigated, and the ethanol titer increased from 4.1 to 7.9 g/L when pulse fed-batch was used instead of batch production, with CelluX™4 performing best. Both strains made use of the xylose isomerase (XI) pathway, with strain TFA7 engineered for increased tolerance against inhibitors. By administering concentrated HSSL in pulses to shake-flask cultures, the ethanol...
Journal of Applied Microbiology, 2008
Aim: To identify fungi that are capable of increasing ethanol production from lignocellulose in spent sulfite liquor. Methods and Results: In a batch fermentation study, the fungal mix could produce 24AE61 g l )1 ethanol using spent sulfite liquor as substrate. The fungal mix grew well on glucose, xylose, hemicellulose and cellulose. In addition, we were able to identify the fungal mix by use of PCR-amplification of DNA and sequencing, and they were identified as Chalara parvispora and Trametes hirsuta ⁄ T. versicolor. In a reconstitution study, the identified fungi were shown to produce equal amount of ethanol as the fungal mix. We were also able to show that C. parvispora could produce ethanol from xylose. Conclusion: The present study has shown that ethanol production from biomass can be increased by use of C. parvispora and T. versicolor when compared with fermentation using only S. cerevisiae.
Enzyme and Microbial Technology, 1996
The inhibitory effects of six lignocellulose degradation products on glucose fermentation by Saccharomyces cerevisiae and Zymomonas mobilis on xylose fermentation by Pichia stipitis and Candida shehatae were studied in batch cultures. Toxic compounds were added in varying concentrations and subsequent inhibitions on growth and ethanol production were quantified. Vanillin was shown to be a strong inhibitor of both growth and ethanol production by xylose fermenting yeasts and S. cerevisiae when it was added to the culture media at a concentration of 1 g l−1. Fermentative activities of Z. mobilis were greatly sensitive to the presence of hydroxybenzaldehyde (0.5 g l−1). Analysis of culture media extracts showed that some of the inhibitors, particularly vanillin and furaldehyde, could be assimilated by the tested microbial strains which resulted in the partial recovery in both growth and ethanol production processes on prolonged incubation.
Applied Biochemistry and Biotechnology, 2007
Spent sulfite pulping liquor (SSL) contains lignin, which is present as lignosulfonate, and hemicelluloses that are present as hydrolyzed carbohydrates. To reduce the biological oxygen demand of SSL associated with dissolved sugars, we studied the capacity of Pichia stipitis FPL-YS30 (xyl3Δ) to convert these sugars into useful products. FPL-YS30 produces a negligible amount of ethanol while converting xylose into xylitol. This work describes the xylose fermentation kinetics of yeast strain P.stipitis FPL-YS30. Yeast was grown in rich medium supplemented with different carbon sources: glucose, xylose, or ammonia-base SSL. The SSL and glucose-acclimatized cells showed similar maximum specific growth rates (0.146 h −1). The highest xylose consumption at the beginning of the fermentation process occurred using cells precultivated in xylose, which showed relatively high specific activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49). However, the maximum specific rates of xylose consumption (0.19 g xylose /g cel h) and xylitol production (0.059 g xylitol /g cel h) were obtained with cells acclimatized in Prepared for 29th Symposium on Biotechnology for Fuels and Chemicals.
Applied Microbiology and Biotechnology, 2004
An overview of the different inhibitors formed by pre-treatment of lignocellulosic materials and their inhibition of ethanol production in yeast and bacteria is given. Different high temperature physical pre-treatment methods are available to render the carbohydrates in lignocellulose accessible for ethanol fermentation. The resulting hydrolyzsates contain substances inhibitory to fermentation—depending on both the raw material (biomass) and the pre-treatment applied.
Fermentation of lignocellulose hydrolysates with yeasts and xylose isomerase
Enzyme and Microbial Technology, 1989
Untreated spent sulfite liquor (SSL) was fermented with five yeasts, Candida tropicalis, Pichia stipitis, Pachysolen tannophilus, Schizosaccharomyces pombe, Saccharomyces cerevisiae, and a co-culture of P. tannophilus and S. cerevisiae, in the presence of commercial xylose (glucose) isomerases and 4.6 mM azide. The highest yield of ethanol, 0.41 g g ~ total sugar, was obtained with S. cerevisiae. The yield based on consumed sugars and per gram cell dry weight was also highest with this yeast. C. tropicalis and P. tannophilus produced considerable amounts of polyoles, mainly xylitol. With P. stipitis sugar uptake was rapidly inhibited in untreated SSL. The presence of azide contributed to the yield by about 0.04, mainly due to the fermentation of stored carbohydrates. The fermentation of hydrogen fluoride-pretreated and acid-hydrolysed wheat straw with S. cerevisiae, xylose isomerase, and azide gave a yield of O.40 g ethanol g-Z total sugar. In this substrate the xylose utilization was 84% compared with 51% in SSL, which is discussed in relation to the salt sensitivity of xylose isomerases.
Biotechnology for Biofuels, 2019
Abstract Background: Lignocellulosic hydrolysates contain a mixture of hexose (C6)/pentose (C5) sugars and pretreatmentgenerated inhibitors (furans, weak acids and phenolics). Therefore, robust yeast isolates with characteristics of C6/C5 fermentation and tolerance to pretreatment-derived inhibitors are pre-requisite for efficient lignocellulosic material based biorefineries. Moreover, use of thermotolerant yeast isolates will further reduce cooling cost, contamination during fermentation, and required for developing simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SScF), and consolidated bio-processing (CBP) strategies. Results: In this study, we evaluated thirty-five yeast isolates (belonging to six genera including Saccharomyces, Kluyveromyces, Candida, Scheffersomyces, Ogatea and Wickerhamomyces) for pretreatment-generated inhibitors {furfural, 5-hydroxymethyl furfural (5-HMF) and acetic acid} and thermotolerant phenotypes along with the fermentation performances at 40 °C. Among them, a sugarcane distillery waste isolate, Saccharomyces cerevisiae NGY10 produced maximum 49.77 ± 0.34 g/l and 46.81 ± 21.98 g/l ethanol with the efficiency of 97.39% and 93.54% at 30 °C and 40 °C, respectively, in 24 h using glucose as a carbon source. Furthermore, isolate NGY10 produced 12.25 ± 0.09 g/l and 7.18 ± 0.14 g/l of ethanol with 92.81% and 91.58% efficiency via SHF, and 30.22 g/l and 25.77 g/l ethanol with 86.43% and 73.29% efficiency via SSF using acid- and alkali-pretreated rice straw as carbon sources, respectively, at 40 °C. In addition, isolate NGY10 also produced 92.31 ± 3.39 g/l (11.7% v/v) and 33.66 ± 1.04 g/l (4.26% v/v) ethanol at 40 °C with the yields of 81.49% and 73.87% in the presence of 30% w/v glucose or 4× concentrated acid-pretreated rice straw hydrolysate, respectively. Moreover, isolate NGY10 displayed furfural- (1.5 g/l), 5-HMF (3.0 g/l), acetic acid- (0.2% v/v) and ethanol-(10.0% v/v) tolerant phenotypes. Conclusion: A sugarcane distillery waste isolate NGY10 demonstrated high potential for ethanol production, C5 metabolic engineering and developing strategies for SSF, SScF and CBP. Keywords: Thermo-tolerance, Inhibitors, SHF, SSF, Fermentation, Ethanol
Special Topics in Renewable Energy Systems, 2018
The world faces a progressive depletion of its energy resources, mainly fossil fuels based on non-renewable resources. At the same time, the consumption of energy grows at high rates, and the intensive use of fossil fuels has led to an increase in the generation of gaseous pollutants released into the atmosphere, which has caused changes in the global climate. The lignocellulosic bioethanol is considered as a promising alternative for use as fuel ethanol. However, one of the main problems in producing ethanol is toxic compounds generated during hydrolysis of lignocellulosic wastes; these compounds cause a longer lag phase and irreversible cell damage to the microorganisms used in the fermentation step. These conditions of fermentation affect the productivity and the economic feasibility of the lignocellulosic ethanol production process. In this context, many efforts had been carried out to improve the capacity of volumetric ethanol productivity of the yeast. The yeast Saccharomyces cerevisiae is commonly employed in industrial ethanol production. However non-Saccharomyces yeast as Kluyveromyces marxianus can produce alcohols at similar or higher levels than S. cerevisiae and on inhibitory conditions.
Ethanol and Biomass Production from Spent Sulfite Liquor by Filamentous Fungi
World Academy of Science, Engineering and Technology, International Journal of Biological, Biomolecular, Agricultural, Food and Biotechnological Engineering, 2017
Since filamentous fungi are capable of assimilating several types of sugars (hexoses and pentoses), they are potential candidates for bioconversion of spent sulfite liquor (SSL). Three filamentous fungi such as Aspergillus oryzae, Mucor indicus, and Rhizopus oryzae were investigated in this work. The SSL was diluted in order to obtain concentrations of 50, 60, 70, 80, and 90% and supplemented with two types of nutrients. The results from cultivations in shake flask showed that A. oryzae and M. indicus were not able to grow in pure SSL and SSL90% while R. oryzae could grow only in SSL50% and SSL60%. Cultivation with A. oryzae resulted in the highest yield of produced fungal biomass, while R. oryzae cultivation resulted in the lowest fungal biomass yield. Although, the mediums containing yeast extract, (NH4)2SO4, KH2PO4, CaCl2∙2H2O, and MgSO4∙7H2O as nutrients supplementations produced higher fungal biomass compared to the mediums containing NH4H2PO4 and ammonia, but there was no sign...
Asian Journal of Chemistry
Industrial lignocellulosic bioethanol processes are exposed to different environmental stresses (such as inhibitor compounds, high temperature, and high solid loadings). In this study, a systematic approach was followed where the liquid and solid fractions were mixed to evaluate the influence of varied solid loadings, and different percentages of liquor were used as liquid fraction to determine inhibitor effect. Ethanol production by simultaneous saccharification and fermentation (SSF) of hydrothermally pretreated Eucalyptus globulus wood (EGW) was studied under combined diverse stress operating conditions (30-38°C, 60-80 g of liquor from hydrothermal treatment or autohydrolysis (containing inhibitor compounds)/100 g of liquid and liquid to solid ratio between 4 and 6.4 g liquid in SSF/g unwashed pretreated EGW) using an industrial Saccharomyces cerevisiae strain supplemented with low-cost byproducts derived from agro-food industry. Evaluation of these variables revealed that the combination of temperature and higher solid loadings was the most significant variable affecting final ethanol concentration and cellulose to ethanol conversion, whereas solid and autohydrolysis liquor loadings had the most significant impact on ethanol productivity. After optimization, an ethanol concentration of 54 g/L (corresponding to 85 % of conversion and 0.51 g/Lh of productivity at 96 h) was obtained at 37°C using 60 % of autohydrolysis liquor and 16 % solid loading (liquid to solid ratio of 6.4 g/g). The selection of a suitable strain along with nutritional supplementation enabled to produce noticeable ethanol titers in quite restrictive SSF operating conditions, which can reduce operating cost and boost the economic feasibility of lignocellulose-to-ethanol processes.