Semi-simultaneous Saccharification Research Articles

Enhanced fermentability of poplar by combination of alkaline peroxide pretreatment and semi-simultaneous saccharification and fermentation.

To improve ethanol productivity with few inhibitors generated, a novel process of combined alkaline peroxide (AP) pretreatment and semi-simultaneous saccharification and fermentation (SSSF) was developed in this work. Pretreatment with 10% (g H2O2/g wood) H2O2 at 160°C for 2h followed by SSSF was found to be the optimal combination with remarkably increased ethanol yield. The proposed process resulted in 63.1% of ethanol yield, which was about five times more than that of the untreated sample that was processed using conventional simultaneous saccharification and fermentation (SSF). The efficient conversion was ascribed to the high delignification efficiency (64.9%) of AP pretreatment, which led to incompact structure and generation of fewer inhibitors during SSSF (c. 6g/L of lactic acid) than SSF (c. 10 g/L of lactic acid). This combined approach was proved to be an effective method for the promotion of the bioconversion of lignocellulosic materials.

Comparison of delignified coconuts waste and cactus for fuel-ethanol production by the simultaneous and semi-simultaneous saccharification and fermentation strategies

It is of the highest importance to study different alternatives/strategies as simultaneous (SSF) and semi-simultaneous (SSSF) saccharification and fermentation process, as well as the prospects of the utilization of lignocellulosic residues as raw materials for fuel-ethanol production. In the first part of this work, different raw materials (cactus (CAC), green coconut shell (GCS), mature coconut fibre (MCF) and mature coconut shell (MCS)) were pretreated by sequential alkaline hydrogen peroxide (Alk-H2O2)–sodium hydroxide (NaOH) process. The characterization of the obtained solids by FTIR, SEM, X-ray and crystallinity indexes confirmed the higher susceptibility of these pretreated materials to enzymatic action. These results were further confirmed by the corresponding glucose conversion yields – 68.44%, 70.20%, 76.21% and 74.50% for CAC, GCS, MCF and MCS, respectively. Subsequently, the comparison between SSF and SSSF using Saccharomyces cerevisiae, Pichia stipitis, Zymomonas mobilis and pretreated MCF (selected in the enzymatic hydrolysis step) was done, being shown that a short presaccharification step at 50°C for 8h in the SSSF had a positive effect on the overall ethanol yield, with an increase from 79.27–84.64% to 85.04–89.15%. In all the cases, the SSSF strategy allowed the obtention of higher ethanol concentrations than SSF.

Characteristics of corn stover pretreated with liquid hot water and fed-batch semi-simultaneous saccharification and fermentation for bioethanol production.

Corn stover is a promising feedstock for bioethanol production because of its abundant availability in China. To obtain higher ethanol concentration and higher ethanol yield, liquid hot water (LHW) pretreatment and fed-batch semi-simultaneous saccharification and fermentation (S-SSF) were used to enhance the enzymatic digestibility of corn stover and improve bioconversion of cellulose to ethanol. The results show that solid residues from LHW pretreatment of corn stover can be effectively converted into ethanol at severity factors ranging from 3.95 to 4.54, and the highest amount of xylan removed was approximately 89%. The ethanol concentrations of 38.4 g/L and 39.4 g/L as well as ethanol yields of 78.6% and 79.7% at severity factors of 3.95 and 4.54, respectively, were obtained by fed-batch S-SSF in an optimum conditions (initial substrate consistency of 10%, and 6.1% solid residues added into system at the prehydrolysis time of 6 h). The changes in surface morphological structure, specific surface area, pore volume and diameter of corn stover subjected to LHW process were also analyzed for interpreting the possible improvement mechanism.

Tween 40 pretreatment of unwashed water-insoluble solids of reed straw and corn stover pretreated with liquid hot water to obtain high concentrations of bioethanol

BackgroundLiquid hot water (LHW) pretreatment is an effective and environmentally friendly method to produce bioethanol with lignocellulosic materials. In our previous study, high ethanol concentration and ethanol yield were obtained from water-insoluble solids (WIS) of reed straw and corn stover pretreated with LHW by using fed-batch semi-simultaneous saccharification and fermentation (S-SSF). However, high cellulase loading and the large amount of wash water possibly limit the practical application of LHW pretreatment. To decrease cellulase loading and the amount of wash water, we performed Tween 40 pretreatment before WIS was subjected to bioethanol fermentation.ResultsResults showed that the optimum conditions of Tween 40 pretreatment were as follows: Tween 40 concentration of 1.5%, WIS-to-Tween 40 ratio of 1:10 (w/v), and pretreatment time of 1 hour at ambient temperature. After Tween 40 pretreatment, cellulase loading could be greatly reduced. After Tween 40 pretreatment, the residual liquid could be recycled for utilization but slightly affected ethanol concentration and yield. The unwashed WIS could obtain a high ethanol concentration of 56.28 g/L (reed straw) and 52.26 g/L (corn stover) by Tween 40 pretreatment using fed-batch S-SSF. Ethanol yield reached a maximum of 69.1% (reed straw) and 71.1% (corn stover).ConclusionsTween 40 pretreatment was a very effective and less costly method with unwashed WIS. This pretreatment could greatly reduce cellulase loading and save wash water. Higher ethanol concentration was obtained almost without reducing ethanol yield.

Fed-batch semi-simultaneous saccharification and fermentation of reed pretreated with liquid hot water for bio-ethanol production using Saccharomyces cerevisiae

Reed was pretreated with liquid hot water (LHW) and then subjected to fed-batch semi-simultaneous saccharification and fermentation (S-SSF) to obtain high ethanol concentration and yield. Results show that water-insoluble solid (WIS) produced from reed pretreated at 180 and 210°C could be effectively converted to ethanol by using Saccharomyces cerevisiae. The optimum conditions for bio-ethanol production are as follows: fermentation temperature of 36°C, pH of 4.8 with cellulase loading of 40 filter paper activity units/g oven-dried WIS, and 18 h pre-hydrolysis at 50°C. Approximately 6.4% (w/v) fed-batch substrate was added after 6 h of the 18 h enzymatic pre-hydrolysis. The highest ethanol concentration of 39.4 g/L was achieved. The conversion of glucan in the WIS to ethanol reached 79.1% (180°C) and 75.1% (210°C) respectively. The ethanol yields per kg of oven-dried reed were 283 g/L at 180°C and 244 g/L at 210°C.

High concentrations of cellulosic ethanol achieved by fed batch semi simultaneous saccharification and fermentation of waste-paper

A fundamental goal of second generation ethanol production is to increase the ethanol concentration to 10% (v/v) or more to optimise distillation costs. Semi simultaneous saccharification and fermentations (SSSF) were conducted at small pilot scale (5L) utilising fed-batch additions of solid shredded copier paper substrate. Early addition of Accellerase® 1500 at 16FPU/g substrate and 30U/g β-glucosidase followed by substrate only batch addition allowed low final equivalent enzyme concentrations to be achieved (3.7FPU/g substrate) whilst maintaining digestion. Batch addition resulted in a cumulative substrate concentration equivalent to 65% (w/v). This in turn resulted in the production of high concentrations of ethanol (11.6% v/v). The success of this strategy relied on the capacity of the bioreactor to perform high shear mixing as required. Further research into the timing and number of substrate additions could lead to further improvement in overall yields from the 65.5% attained.

Enhanced bio-ethanol production from cellulosic materials by semi-simultaneous saccharification and fermentation using high temperature resistant Saccharomyces cerevisiae TJ14

The capability of multi-stress-tolerant Saccharomyces cerevisiae diploid strain TJ14 for the production of cellulosic bio-ethanol by semi-simultaneous saccharification and fermentation (SSSF) technology was evaluated under high-temperature conditions. At 39°C, the TJ14 produced 45 g/l ethanol by SSSF of 100 g (w/v)/l cellulose - a significantly higher concentration than reported in prevailing literature.

Ethanol production of semi-simultaneous saccharification and fermentation from mixture of cotton gin waste and recycled paper sludge

Ethanol production from the steam-exploded mixture of 75% cotton gin waste and 25% recycled paper sludge in various conditions was investigated by semi-simultaneous saccharification and fermentation (SSSF) consisting of a pre-hydrolysis and a simultaneous saccharification and fermentation (SSF). Four cases were studied: 24-h pre-hydrolysis + 48-h SSF (SSSF 24), 12-h pre-hydrolysis + 60-h SSF (SSSF 12), 72-h SSF, and 48-h hydrolysis + 24-h fermentation (SHF). The ethanol concentration, yield, and productivity of SSSF 24 were higher than those of the other operations. A model of SSF was used to simulate the data for four components in SSF. The analysis of the reaction rates of cellobiose, glucose, cell, and ethanol using the model and the parameters from the experiments showed that there was a transition point of the rate-controlling step at which the cell growth control in the initial 2 h was changed to the cellobiose reaction control in later period during ethanol production of SSF from the mixture.

Modeling semi-simultaneous saccharification and fermentation of ethanol production from cellulose

Using a highly refined standard cellulose (microcrystalline cellulose, (Avicel PH101)), the kinetics of the simultaneous saccharification and fermentation (SSF) of cellulose to ethanol was studied with a prior hydrolysis phase (semi-simultaneous saccharification and fermentation (SSSF)) conducted under optimal conditions for enzymatic hydrolysis. Four cases have been studied: 24-h pre-hydrolysis + 48-h SSF (SSSF 24), 12-h pre-hydrolysis + 60-h SSF (SSSF 12), 72-h SSF, and 48-h hydrolysis + 24-h fermentation. SSSF 24 produced higher yield and higher productivity of ethanol than the other operating modes. A coupled set of differential equations were developed to describe the change rates of cellobiose, glucose, microorganism, ethanol, glycerol, acetic acid, and lactic acid concentrations in the batch operation of separate hydrolysis and SSF of ethanol production from Avicel PH101. The model parameters were determined by a MATLAB program based on the batch experimental data of the SSSF. The analysis of the reaction rates of cellobiose, glucose, cell, and ethanol using the model showed that the conversion of cellulose to cellobiose was the rate-controlling step in the SSSF process of ethanol production from cellulose. The batch SSSF model was extended to the continuous and fed-batch operating modes. For the continuous operation in the SSSF, the productivity of SSSF 24 was much higher than that of SSSF 12 though the ethanol concentrations of both cases have not a great difference.