• Journal of Microbiology and Biotechnology
• /
• v.9 no.3
• /
• pp.297-302
• /
• 1999

Simultaneous saccharification and fermentation (SSF) experiments were carried out with a lignocellulosic biomass. The effects of temperature on enzymatic saccharification and the ethanol fermentation were also investigated. The batch SSF process gave a final ethanol concentration of 10.44 g/l and equivalent glucose yield of 0.55 g/g, which was increased by 67％ or higher over the saccharification at 42℃. The optimal operating condition was found to vary in several parameters, such as the transmembrane pressure, permeation rate, and separation coefficient, related to the SSF combined with membrane system (semi-batch system). When the fermentation was operated in a semi-batch mode, the efficiency of the enzymes and yeast lasted three times longer than in a batch mode.

• Journal of Microbiology and Biotechnology
• /
• v.16 no.9
• /
• pp.1355-1361
• /
• 2006

The simultaneous saccharification and fermentation (SSF) process consists of concurrent enzymatic saccharification and fermentation. In the present cybernetic model, the saccharification process, which is based on the modified Michaelis-Menten kinetics and enzyme inhibition kinetics, was combined with the fermentation process, which is based on the Monod equation. The cybernetic modeling approach postulates that cells adapt to utilize the limited resources available to them in an optimal way. The cybernetic modeling was suitable for describing sequential growth on multiple substrates by Brettanomyces custersii, which is a glucose- and cellobiose-fermenting yeast. The proposed model was able to elucidate the SSF process in a systematic manner, and the performance was verified by previously published data.

• KSBB Journal
• /
• v.25 no.6
• /
• pp.565-571
• /
• 2010

To develop thermostable ethanol fermentative yeast strain for lignocellulosic simultaneous saccharification and fermentation, high ethanol producing yeast, Saccharomyces cerevisiae CHY1012 and thermostable yeast, Kluyveromyces marxianus CHY1703 were fused by protoplast fusion. The thermostable fusant, CHY1612 was identified as a Kluyveromyces marxianus by phenotypic and physiological characteristics, as well as molecular analysis based on the D1/D2 domains of the large subunit (26S) rDNA gene and the internally transcribed spacer (ITS) 1 + 2 regions. For lignocellulosic ethanol production, AFEX pretreated barley straw at $150^{\circ}C$ for 90 min was used in a simultaneous saccharification and fermentation (SSF) process using thermotolerant CHY1612. The SSF from 16% pretreated barley straw at $43^{\circ}C$ gave a saccharification ratio of 90.5%, a final ethanol concentration of 38.5 g/L, and a theoretical yield of 91.2%. These results show that K. marxianus CHY1612 has potential for lignocellulosic ethanol production through simultaneous saccharification and fermentation with further development of process.

• Journal of Microbiology and Biotechnology
• /
• v.21 no.7
• /
• pp.703-710
• /
• 2011

Enzymatic saccharification of corn stover using Phanerochaete chrysosporium and Gloeophyllum trabeum and subsequent fermentation of the saccharification products to ethanol by Saccharomyces cerevisiae and Escherichia coli K011 were achieved. Prior to simultaneous saccharification and fermentation (SSF) for ethanol production, solid-state fermentation was performed for four days on ground corn stover using either P. chrysosporium or G. trabeum to induce in situ cellulase production. During SSF with S. cerevisiae or E. coli, ethanol production was the highest on day 4 for all samples. For corn stover treated with P. chrysosporium, the conversion to ethanol was 2.29 g/100 g corn stover with S. cerevisiae as the fermenting organism, whereas for the sample inoculated with E. coli K011, the ethanol production was 4.14 g/100 g corn stover. Corn stover treated with G. trabeum showed a conversion 1.90 and 4.79 g/100 g corn stover with S. cerevisiae and E. coli K011 as the fermenting organisms, respectively. Other fermentation co-products, such as acetic acid and lactic acid, were also monitored. Acetic acid production ranged between 0.45 and 0.78 g/100 g corn stover, while no lactic acid production was detected throughout the 5 days of SSF. The results of our experiment suggest that it is possible to perform SSF of corn stover using P. chrysosporium, G. trabeum, S. cerevisiae and E. coli K011 for the production of fuel ethanol.

• KSBB Journal
• /
• v.13 no.1
• /
• pp.38-43
• /
• 1998

Application of pervaporative extraction of ethanol to simultaneous saccharification and fermentation(SSF) of cellulose was investigated. From batch experiments, optimum cellulose substrate and enzyme loadings were found to be 10% and 15 IFPU/g cellulose, respectively. The cellulose conversion was lowered in fed-batch system due to the ethanol accumulation. The activity of the yeast Saccharomyces uvarum used in this study was significantly reduced at ethanol concentrations above around 40 g/L. From pervaporation experiments using PDMS membrane, ethanol was efficiently separated at 38$^\circ C$ and 10 mmHg of a down stream pressure. The pervaporation unit with 240 cm$^2$ of surface area was combined into the SSF reactor. The continuous removal of ethanol by pervaporation during SSF resulted in an improved cellulose conversion. Within the scope of this experiment, ethanol yields in the pervaporative SSF and simple SSF were 68.3% and 56.6%, respectively. The permeate flux for SSF broth pervaporation was about one-half that for the pervaporation of aqueous ethanol solution. Accordingly, the development of a membrane with higher ethanol selectivity and flux will increase the feasibility of this technology.

• Microbiology and Biotechnology Letters
• /
• v.16 no.3
• /
• pp.213-218
• /
• 1988

Studies were made to optimize the simultaneous saccharification and fermentation (SSF) of rice straw to produce butanol using Clostridium acetobutylicum KCTC 1037 and a cellulolytic enzyme preparation from Trichoderma viride. The fermentation was inhibited when the liquid enzyme preparation from Novo was used, whilst a successful fermentation was achieved in the SSF using the enzyme manufactured by Pacific Chemical Co. The minimum cellulase concentration for the successful fermentation of pure cellulose was found to be 4 IU/g of substrate used. Alkaline treatment was better method for the fermentation of rice straw by the system. SSF using 25％ alkaline treated rice straw produced 150 mM butanol, 90 mM acetone. On the other hand, fermentation of ball milled rice straw was mainly acidogenic producing 98 mM acetate and 64 mM butyrate with less than 20 mM butanol. These results show that rice straw contains (a) specific inhibitor(s) for solventogenesis which is destroyed or soluble in alkali.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.1
• /
• pp.40-47
• /
• 2005

Modeling and simulation for simultaneous saccharification and fermentation (SSF) process in bioconversion of paper mill sludge to lactic acid was carried out. The SSF process combined the enzymatic hydrolysis of paper mill sludge into glucose and the fermentation of glucose into lactic acid in one reactor. A mathematical modeling for cellulose hydrolysis was developed, based on the proposed mechanism of cellulase adsorption deactivation. Another model for simple lactic acid fermentation was also made. A whole mathematical model for SSF was developed by combining the above two models for cellulose hydrolysis and lactic acid fermentation. The characteristics of the SSF process were investigated using the mathematical model.

• Microbiology and Biotechnology Letters
• /
• v.11 no.3
• /
• pp.181-185
• /
• 1983

The possibility of the ethanol fermentation from raw cassava starch without cooking was investigated. Saccharification yield in the simultaneous saccharification-fermentation (SSF) system was compared with that in saccharification of raw cassava starch, using glucoamylase of Aspergillus shirousmi. Although the saccharification yield of raw cassava starch with 10 folds of the enzyme was 60% compared to cooked cassava starch, higher saccharification could be obtained by SSF This result is maybe due to the elimination of end product inhibition in saccharification of raw starch by glucoamylase. Final ethanol yield from raw cassava starch was about 88% under the condition of 3$0^{\circ}C$, 120 rpm shaking after 3 days in the SSF system.

• Korean Journal of Microbiology
• /
• v.26 no.3
• /
• pp.278-282
• /
• 1988

Rice straw was used in the acetone-butanol fermentation by semultaneous saccharification and fermentation (SSF) using Clostridium acetobutylicum and cellulolytic enzyme. Over 230 mM of solvent was produced from alkali treated rice straw of from ball-milled microcrystalline cellulose whilst only acidic fermentation products were formed from ball-milled rice straw. From the results it is concluded that rice straw used in the study contained an inhibitor for the solventogenesis by the organism which is insoluble in water and some organic solvent and destroyed by alkaline treatment.

• KSBB Journal
• /
• v.30 no.3
• /
• pp.125-131
• /
• 2015

Kluyveromyces marxianus is a well-known thermotolerant yeast. Although Saccharomyces cerevisiae is the most commonly used yeast species for ethanol production, the thermotolerant K. marxianus is more suitable for simultaneous saccharification and fermentation (SSF) processes. This is because enzymatic saccharification usually requires a higher temperature than that needed for the optimum growth of S. cerevisiae. In this study, we compared the fermentation patterns of S. cerevisiae and K. marxianus under various temperatures of fermentation. The results show that at a fermentation temperature of $45^{\circ}C$, K. marxianus exhibited more than two fold higher growth rate and ethanol production rate in comparison to S. cerevisiae. For SSF using starch or corn stover as the sole carbon source by K. marxianus, the high temperature ($45^{\circ}C$) fermentations showed higher enzymatic activities and ethanol production compared to SSF at $30^{\circ}C$. These results demonstrate the potential of the thermotolerant yeast K. marxianus for SSF in the industrial production of biofuels.