• New & Renewable Energy
• /
• v.9 no.1
• /
• pp.25-32
• /
• 2013

It is indispensable to increase the conversion rate of a reducing sugars such as pentose and hexose derived from cellulosic wastes for a highly efficient bioethanol fermentation from food wastes. The saccharification liquid from cellulosic substrates such as vegetable food wastes contained lots of hexose like glucose and pentose like xylose. Since Saccharomyces-based yeasts could not convert xylose to bioethanol, Pichia stipitis which could directly ferment xylose to ethanol was chosen. After selecting Saccharomyces coreanus and P. stipitis, fermentation characteristics by mixture of two yeasts were investigated. As a result, it was verified the production of ethanol was enhanced by the co-fermentation, although there were somewhat differences between the fermentation characteristics by the aeration methods. Moreover, the consumption of pentose, hexose and disaccharide was obviously observed, and aeration in the process of fermentation seemed to stimulate the activity of P. stipitis.

• Applied Chemistry for Engineering
• /
• v.25 no.6
• /
• pp.619-623
• /
• 2014

The acid hydrolysis and enzymatic saccharification were carried out for the production of cellulosic ethanol. The possibility of bio-energy production from tangerine peel and apple and watermelon rind was evaluated by determining the optimum production condition. The optimum conditions for the production of cellulosic ethanol from fruit peel were as follows: the sulfuric acid concentration and reaction time of acid hydrolysis for the ethanol production from an apple rind were 20 wt% and 90 min, respectively. The concentration of sulfuric acid for tangerine peel and a watermelon rind at the hydrolysis time of 60 min were 15 wt% and 10 wt%, respectively. A viscozyme was proven as the best conversion for the ethanol production when using enzymatic saccharification from fruit peels. The optimum enzymatic saccharification time for tangerine peel and apple and watermelon rind were 60, 180, and 120 min, respectively.

• Journal of Microbiology and Biotechnology
• /
• v.27 no.9
• /
• pp.1649-1656
• /
• 2017

In simultaneous saccharification and fermentation (SSF) for production of cellulosic biofuels, engineered Saccharomyces cerevisiae capable of fermenting cellobiose has provided several benefits, such as lower enzyme costs and faster fermentation rate compared with wild-type S. cerevisiae fermenting glucose. In this study, the effects of an alternative intracellular cellobiose utilization pathway-a phosphorolytic pathway based on a mutant cellodextrin transporter (CDT-1 (F213L)) and cellobiose phosphorylase (SdCBP)-was investigated by comparing with a hydrolytic pathway based on the same transporter and an intracellular ${\beta}$-glucosidase (GH1-1) for their SSF performances under various conditions. Whereas the phosphorolytic and hydrolytic cellobiose-fermenting S. cerevisiae strains performed similarly under the anoxic SSF conditions, the hydrolytic S. cerevisiae performed slightly better than the phosphorolytic S. cerevisiae under the microaerobic SSF conditions. Nonetheless, the phosphorolytic S. cerevisiae expressing the mutant CDT-1 showed better ethanol production than the glucose-fermenting S. cerevisiae with an extracellular ${\beta}$-glucosidase, regardless of SSF conditions. These results clearly prove that introduction of the intracellular cellobiose metabolic pathway into yeast can be effective on cellulosic ethanol production in SSF. They also demonstrate that enhancement of cellobiose transport activity in engineered yeast is the most important factor affecting the efficiency of SSF of cellulose.

• Korean Chemical Engineering Research
• /
• v.59 no.1
• /
• pp.54-59
• /
• 2021

The pretreatment of cellulosic biomass is essentially needed because it has more lignin compared with a starch biomass. Ethanol as an organosolv for pretreatment can easily separate some components which can inhibit enzymatic hydrolysis and be re-usuable by distillation. The flow-through process have some strength, separating components continuously, development for scale up. In this research, two-kinds (wheat straw, miscanthus) of biomass was pretreated for development of enzymatic hydrolysis by adoption of pretreatment process of corn stover.

• KSBB Journal
• /
• v.23 no.1
• /
• pp.1-7
• /
• 2008

The world demand of ethanol as an alternative fuel for gasoline is increasing rapidly because of high oil price and global climate change. Most of ethanol is currently produced from corn grain or sugars in sugarcane and sugar beet. Because these sources compete with foods and animal feed and are not expected to be enough for future demand of ethanol. Thus, cellulosic ethanol from agricultural residues or wood has to be commercialized in near future. Typical cellulosic ethanol production consists of pretreatment, enzyme hydrolysis, fermentation and product separation. This paper reviews the principles and status of each step and discusses issues for cellulosic ethanol production.

• Journal of Microbiology and Biotechnology
• /
• v.24 no.9
• /
• pp.1280-1290
• /
• 2014

In order to obtain the cellulolytic bacterial consortia, sediments from Great Basin hot springs (Nevada, USA) were sampled and enriched with cellulosic biomass as the sole carbon source. The bacterial composition of the resulting anaerobic ethanol-producing celluloytic bacterial consortium, named SV79, was analyzed. With methods of the full-length 16S rRNA library-based analysis and denaturing gradient gel electrophoresis, 21 bacteria belonging to eight genera were detected from this consortium. Clones with closest relation to the genera Acetivibrio, Clostridium, Cellulosilyticum, Ruminococcus, and Sporomusa were predominant. The cellulase activities and ethanol productions of consortium SV79 using different agricultural residues (sugarcane bagasse and spent mushroom substrate) and energy crops (Spartina anglica, Miscanthus floridulus, and Pennisetum sinese Roxb) were studied. During cultivation, consortium SV79 produced the maximum filter paper activity (FPase, 9.41 U/ml), carboxymethylcellulase activity (CMCase, 6.35 U/ml), and xylanase activity (4.28 U/ml) with sugarcane bagasse, spent mushroom substrate, and S. anglica, respectively. The ethanol production using M. floridulus as substrate was up to 2.63 mM ethanol/g using gas chromatography analysis. It has high potential to be a new candidate for producing ethanol with cellulosic biomass under anoxic conditions in natural environments.

• Microbiology and Biotechnology Letters
• /
• v.19 no.4
• /
• pp.325-330
• /
• 1991

In order to develop yeast strains which can effectively produce ethanol from cellulosic hydrolyzates, protoplast fusion between Candida sp. KM-09-135 and Saccharomyces cweoisiue SM-07 was carried out and obtained the excellent fusant KMS-23. Fusant KMS-23 showed the optimal growth temperature and ethanol productivity at $37^{\circ}C$, and assimilated xylose, cellobiose, maltose and raffinose as fermentative sugars. Cell size of the fusant was about 1.2 times greater than that of KM-09-135 and 1.5 times SM-07. DNA content of fusant was 1.3 times higher than that of SM-07 and similar with KM-09-135. Fusant KMS-23 produced 2.57% (v/v) ethanol from saccharified wheat bran containing 6.44% (w/v) of reducing sugar, which was 1.3 times higher than parent strains under the same conditions.

• 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.

• Journal of Microbiology and Biotechnology
• /
• v.29 no.4
• /
• pp.617-624
• /
• 2019

Bacterial nanocellulose (BNC) which is generally synthesized by several species of bacteria has a wide variety of industrial uses, particularly in the food and material industries. However, the low levels of BNC production during the fermentation process should be overcome to reduce its production cost. Therefore, in this study, we screened and identified a new cellulose-producing bacterium, optimized production of the cellulose, and investigated the morphological properties of the cellulosic materials. Out of 147 bacterial isolates from ripened fruits and traditional vinegars, strain SFCB22-18 showed the highest capacity for BNC production and was identified as Komagataeibacter sp. based on 16S rRNA sequence analysis. During 6-week fermentation of the strain using an optimized medium containing 3.0% glucose, 2.5% yeast extract, 0.24% acetic acid, 0.27% $Na_2HPO_4$, and 0.5% ethanol at $30^{\circ}C$, about 5 g/l of cellulosic material was produced. Both imaging and IR analysis proved that the produced cellulose would be nanoscale bacterial cellulose.

• Microbiology and Biotechnology Letters
• /
• v.47 no.4
• /
• pp.565-573
• /
• 2019

Production of biofuels and value-added materials from cellulosic biomass requires the development of a microbial strain capable of efficiently fermenting mixed sugars. In this study, the natural xylose fermenting yeast, Pichia stipitis, was evolved to simultaneously ferment cellobiose and xylose. Serial subcultures of wild-type P. stipitis in 20 g/l cellobiose were performed to increase the rate of cellobiose consumption. A total of ten rounds of the serial subculture led to the isolation of an evolved strain fermenting cellobiose significantly faster than the parental strain. The evolved strain displayed enhanced ethanol yield from 0 to 0.4 g ethanol/g cellobiose. The evolved P. stipitis simultaneously fermented cellobiose and xylose in batch fermentation. The genetic information of our evolved P. stipitis would be valuable in the development of a microbial host for the production of biofuels and biomaterials from cellulosic biomass.