Simultaneous Saccharification And Fermentation System Research Articles

Effect of amphiphilic lignin derivatives (A-LD) surfactant addition on the fermentation process of sorghum bagasse kraft pulp for bioethanol production

This research was intended to study the effect of Amphiphilic Lignin Derivatives (A-LD) surfactant addition on the bioethanol production by using simultaneous saccharification and fermentation (SSF) system. A-LD synthesis was obtained from single-step lignin isolation from black liquor as a by-product of the Acacia mangium kraft process. This synthesis was carried out by reacting single-step lignin isolation with the polyethylene glycoldiglycidylether (PEDGE), which was heated at 60 °C for one h. SSF was performed by using Saccharomyces cerevisiae InaCC Y93, cellulase enzyme of 50 FPU/g, yeast inoculum in 10% and 20%, and a 15 mg/mL A-LD added into 5.37 g (wet weight) of sweet sorghum bagasse (SSB) kraft pulp. The concentration of reducing sugar and the ethanol contents were analyzed every 24 h for 72 h and also at 89 h. The ethanol concentration, ethanol yield, and the highest percentage of theoretical ethanol yield were 4.91 ± 0.10 g/L, 0.06 ± 0.001 g/g, and 11.29 ± 0.22%, respectively. They were obtained by 20% of yeast inoculum for 24 h fermentation on the SSF system and the addition of A-LD surfactant. The addition of A-LD on the SSF process increased ethanol production and shortened the fermentation time.

Development of a green liquor dregs pretreatment for enhanced glucose recovery from corn cobs and kinetic assessment on various bioethanol fermentation types

This study optimized a novel pretreatment of corn cob wastes (CCW) using green liquor dregs (GLD), a waste product from the chemical kraft pulping industry. Subsequently, the microbial growth and ethanol production kinetics of different bioprocess types were comparatively evaluated using the logistic and modified Gompertz models respectively. The optimized GLD pretreatment conditions released a maximum glucose yield of 0.42 g/g. Separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF) and SSF with pre hydrolysis (PSSF) processes were assessed and gave comparable kinetic data. The SHF and PSSF processes displayed slightly higher microbial and bioethanol kinetic coefficients compared to the SSF system. Implications from this study provide major insights for reducing energy, time and costs incurred with lignocellulosic substrate pretreatment, bioethanol process design and scale up. Additionally, the study demonstrates a possible route for beneficiation of waste material such as GLD.

Stimulatory effects of rhamnolipid on corncob residues ethanol production via high-solids simultaneous saccharification and fermentation

In this study, the feasibility of rhamnolipid-assisted high-solids simultaneous saccharification and fermentation (SSF) of unwashed corncob residues and the process of rhamnolipid action was investigated. The effects of enzyme dosage (5–15 FPU/g-cellulose), inoculation amount (4–12 g/L), and rhamnolipid concentration (0.2–4 g/L) on ethanol production were evaluated. The ethanol yield at 20% (w/w) solids loading and 10 FPU/g-cellulose enzyme dosage increased to 61.99% by adding 0.2 g/L rhamnolipid, which was 22.39% higher than that produced from the control sample with 10 FPU/g-cellulose, and was close to the ethanol yield of the control sample (61.32%) with 15 FPU/g-cellulose. However, adding rhamnolipid at a high dosage (>2 g/L) led to sugar accumulation and negative effects on yeast growth. A schematic showing how rhamnolipid enhancement influences the high-solids SSF revealed that: i) Adding rhamnolipid to the fermentation medium reduced the surface tension of the SSF system; ii) Rhamnolipid accumulated at the interface between the two phases and reduced the level of deactivation of cellulase; and iii) X-ray photoelectron spectroscopy spectra analyses revealed that rhamnolipid addition efficiently reduced the adsorption of the enzyme on fermentation residues. The addition of rhamnolipid is an effective strategy to enhance ethanol production from corncob residues, even without pretreatment.

BUFFER REPLACEMENT AND SIMULTANEOUS SACCHARIFICATION AND FERMENTATION ON BIOBUTANOL PRODUCTION?FROM LIGNOCELLULOSIC BIOMASS

Lignocellulosic biomass is excellent feedstock for biofuel such as biobutanol. Bagasse, rice straw, and empty fruit bunch (EFB) oil palm are untapped potential for biobutanol production as gasoline blending/ substitution. However, biobutanol production by fermentation from lignocellulosic biomass is a process that consumes time and energy which leads to high production costs. This research is intended to optimize biobutanol production that reduces production costs, an important factor on an industrial scale. Optimization is conducted by replacing the buffer solution in enzymatic hydrolysis with distilled water and by using Simultaneous Saccharification and Fermentation (SSF). The results showed that the buffer replacement with distilled water can reduce cost by approximately 41,726 IDR/liter hydrolysate. Biobutanol contents from all biomass of bagasse, rice straw, and EFB oil palm are higher using SSF compared to Separate Hydrolysis and Fermentation (SHF). The SSF system can cut production time by 3 days and save electricity of 32.4 kWh.?

BIOCONVERSION OF POTATO WASTEWATER TO ALCOHOL

This research offers a novel approach for potato wastewater (PW) bioconversion to alcohol by microwaves gelatinization, liquefaction and simultaneous saccharification and fermentation (SSF). Concentrated PW from potato processing to obtain fries was treated by gelatinization, enzymatic hydrolysis through liquefaction and saccharification, and fermentation; a mini-bioreactor was used, with low oxygen, temperature, pH and mixing control. The yeast Saccharomyces cerevisiae and a commercial mix of lactic bacteria were used for fermentations. Two fermentation systems were tested: SSF and saccharification followed by fermentation (SF). The results indicated gelatinization with microwaves at 85oC for 5 minutes as being very efficient on the starch hydrolysis, compared with the classical thermal gelatinization. SF and SSF cultivation systems showed differences in terms of RS production and consumption and ethanol production; the final values after 48 h of cultivation were around 1% RS (both SF and SSF) and 6% ethanol in SF and 7% ethanol in SSF. Yeast and lactic bacteria were not significantly influencing each other at the cultivation on PW and the lactic bacteria showed no influence on the ethanol production. The most adequate strategy was to cultivate only yeast in SSF system at 35oC for 36 hours with production of around 7% ethanol with more than 0.5 g ethanol/g RS.

Mechanistic insight into ultrasound induced enhancement of simultaneous saccharification and fermentation of Parthenium hysterophorus for ethanol production

This paper presents investigations into mechanism of ultrasound assisted bioethanol synthesis using Parthenium hysterophorus biomass through simultaneous saccharification and fermentation (SSF) mode. Approach of coupling experimental results to mathematical model for SSF using Genetic Algorithm based optimization has been adopted. Comparison of model parameters for experiments with mechanical shaking and sonication (10% duty cycle) give an interesting mechanistic account of influence of ultrasound on SSF system. A 4-fold rise in ethanol and cell mass productivity is seen with ultrasound. The analysis reveals following facets of influence of ultrasound on SSF: increase in Monod constant for glucose for cell growth, maximal specific growth rate and inhibition constant of cell growth by glucose and reduction in specific cell death rate. Values of inhibition constant of cell growth by ethanol (K3E), and constants for growth associated (a) and non-growth associated (b) ethanol production remained unaltered with sonication. Beneficial effects of ultrasound are attributed to enhanced cellulose hydrolysis, enhanced trans-membrane transport of substrate and products as well as dilution of the toxic substances due to micro-convection induced by ultrasound. Intrinsic physiological functioning of cells remained unaffected by ultrasound as indicated by unaltered values of K3E, a and b.

A highly efficient β-glucosidase from the buffalo rumen fungus Neocallimastix patriciarum W5

BackgroundCellulose, which is the most abundant renewable biomass on earth, is a potential bio-resource of alternative energy. The hydrolysis of plant polysaccharides is catalyzed by microbial cellulases, including endo-β-1,4-glucanases, cellobiohydrolases, cellodextrinases, and β-glucosidases. Converting cellobiose by β-glucosidases is the key factor for reducing cellobiose inhibition and enhancing the efficiency of cellulolytic enzymes for cellulosic ethanol production.ResultsIn this study, a cDNA encoding β-glucosidase was isolated from the buffalo rumen fungus Neocallimastix patriciarum W5 and is named NpaBGS. It has a length of 2,331 bp with an open reading frame coding for a protein of 776 amino acid residues, corresponding to a theoretical molecular mass of 85.1 kDa and isoelectric point of 4.4. Two GH3 catalytic domains were found at the N and C terminals of NpaBGS by sequence analysis. The cDNA was expressed in Pichia pastoris and after protein purification, the enzyme displayed a specific activity of 34.5 U/mg against cellobiose as the substrate. Enzymatic assays showed that NpaBGS was active on short cello-oligosaccharides from various substrates. A weak activity in carboxymethyl cellulose (CMC) digestion indicated that the enzyme might also have the function of an endoglucanase. The optimal activity was detected at 40°C and pH 5 ~ 6, showing that the enzyme prefers a weak acid condition. Moreover, its activity could be enhanced at 50°C by adding Mg2+ or Mn2+ ions. Interestingly, in simultaneous saccharification and fermentation (SSF) experiments using Saccharomyces cerevisiae BY4741 or Kluyveromyces marxianus KY3 as the fermentation yeast, NpaBGS showed advantages in cell growth, glucose production, and ethanol production over the commercial enzyme Novo 188. Moreover, we showed that the KY3 strain engineered with the NpaNGS gene can utilize 2 % dry napiergrass as the sole carbon source to produce 3.32 mg/ml ethanol when Celluclast 1.5 L was added to the SSF system.ConclusionOur characterizations of the novel β-glucosidase NpaBGS revealed that it has a preference of weak acidity for optimal yeast fermentation and an optimal temperature of ~40°C. Since NpaBGS performs better than Novo 188 under the living conditions of fermentation yeasts, it has the potential to be a suitable enzyme for SSF.

Strategy for simultaneous saccharification and fermentation using a respiratory-deficient mutant of Candida glabrata for bioethanol production

High temperature and agitation are advantageous for ethanol production from insoluble feedstock when using the simultaneous saccharification and fermentation (SSF) technique. To construct an effective SSF system, a respiratory-deficient mutant was isolated from the thermotolerant yeast Candida glabrata. Our results suggest that this respiratory-deficient mutant has higher ethanol production abilities in SSF.

Cellulose ethanol production from waste newsprint by simultaneous saccharification and fermentation using Saccharomyces cerevisiae KNU5377

A thermotolerant ethanol-fermenting yeast, Saccharomyces cerevisiae KNU5377, isolated from a sludge of a local industrial complex stream in Korea, was evaluated for its capability for lignocellulosic ethanol production from waste newsprint in high temperature. In this fermentation, most of dry-defibrated waste newspaper was first saccharified at 50 °C for 108 h using a commercial cellulase and, then with the last addition of dry-defibrated newsprints to the pre-saccharified broth, simultaneous saccharification and fermentation (SSF) of 1.0 L of reaction mixture was carried out at 40 °C, slowly being dropped from 50 °C, for further 72 h in a 5 L fermentor by inoculating the overnight culture of KNU5377. The maximum production of 8.4% (v/v) ethanol was obtained when 250 g (w/v)/L of dry-defibrated waste newspaper was used for ethanol production by SSF. These results suggest that S. cerevisiae KNU5377 is very useful for cellulose ethanol production by the SSF system.

Properties and Performance of Glucoamylases for Fuel Ethanol Production

Studies were conducted on maltodextrin saccharification and on simultaneous saccharification and fermentation (SSF) with various commercial glucoamylases. In kinetics studies, none of the glucoamylases were able to completely convert maltodextrin into glucose. Typically, about 85% conversion was obtained, and glucose yields were about 75%. Typically, the kinetics were biphasic, with 1 h of rapid conversion, then a significant reduction in rate. Data were consistent with strong product inhibition and/or enzyme inactivation. Some glucoamylases followed first-order kinetics, initially slower at dextrin conversion, but eventually achieving comparable conversion and glucose concentrations. Most of the glucoamylases were more active at 55 degrees C than at 35 degrees C, but pH had little effect on activity. Screening studies in an SSF system demonstrated little difference between the glucoamylases, with a few exceptions. Subsequent targeted studies showed clear differences in performance, depending on the fermentation temperature and yeast used, suggesting that these are key parameters that would guide the selection of a glucoamylase.

Bioconversion of cellulose into ethanol by nonisothermal simultaneous saccharification and fermentation.

The kinetic characteristics of cellulase and beta-glucosidase during hydrolysis were determined. The kinetic parameters were found to reproduce experimental data satisfactorily and could be used in a simultaneous saccharification and fermentation (SSF) system by coupling with a fermentation model. The effects of temperature on yeast growth and ethanol production were investigated in batch cultures. In the range of 35-45 degrees C, using a mathematical model and a computer simulation package, the kinetic parameters at each temperature were estimated. The appropriate forms of the model equation for the SSF considering the effects of temperature were developed, and the temperature profile for maximizing the ethanol production was also obtained. Briefly, the optimum temperature profile began at a low temperature of 35 degrees C, which allows the propagation of cells. Up to 10 h, the operating temperature increased rapidly to 39 degrees C, and then decreased slowly to 36 degrees C. In this nonisothermal SSF system with the above temperature profile, a maximum ethanol production of 14.87 g/L was obtained.

Simultaneous saccharification and fermentation of pretreated sugar cane leaves to ethanol

The simultaneous saccharification and fermentation (SSF) of pretreated sugar cane leaves to produce ethanol using a cellulolytic enzyme complex from Trichoderma reesei QM 9414 and Saccharomyces cerevisiae NRRL-Y-132 was optimized. Enzymic saccharification parameters were evaluated prior to SSF studies. A 92% conversion of 2·5% substrate (alkaline hydrogen peroxide pretreated) to sugars was achieved at 50°C and pH 4·5, using T. reesei cellulase (40 FPU/g substrate), in 48 h. The pretreated substrate was then subjected to an SSF process using the cellulase complex and S. cerevisiae cells. Optimization of the SSF system is described.

Continuous fermentation of cellulosic biomass to ethanol

Experimental results are presented for continuous conversion of pretreated hardwood flour to ethanol. A simultaneous saccharification and fermentation (SSF) system comprised ofTrichoderma reesei cellulase supplemented with additional β-glucosidase and fermentation bySaccharomyces cerevisiae was used for most experiments, with data also presented for a direct microbial conversion (DMC) system comprised ofClostridium thermocellum. Using a batch SSF system, dilute acid pretreatment of mixed hardwood at short residence time(10 s, 220°C, 1% H2SO4) was compared to poplar wood pretreated at longer residence time (20 min, 160°C, 0.45% H2SO4). The short residence time pretreatment resulted in a somewhat (10–20%) more reactive substrate, with the reactivity difference particularly notable at low enzyme loadings and/or low agitation. Based on a preliminary screening, inhibition of SSF by byproducts of short residence time pretreatment was measurable, but minor. Both SSF and DMC were carried out successfully in well-mixed continuous systems, with steady-state data obtained at residence times of 0.58–3 d for SSF as well as 0.5 and 0.75 d for DMC. The SSF system achieved substrate conversions varying from 31% at a 0.58-d residence time to 86% at a 2-d residence time. At comparable substrate concentrations (4–5 g/l) and residence times (0.5–0.58 d), substrate conversion in the DMC system (77%) was significantly higher than that in the SSF system (31%). Our results suggest that the substrate conversion in SSF carried out in CSTR is relatively insensitive to enzyme loading in the range 7–25 U/g cellulose and to substrate concentration in the range of 5–60 g/L cellulose in the feed.

Ethanol production from jerusalem artichoke by inulinase and zymomonas mobilis

Ethanol production from Jerusalem artichoke was studied using inulinase and Z.mobilis by simultaneous saccharification and fermentation (SSF) process. The SSF process showed higher ethanol yield and productivity than the acid or enzymatic prehydrolyzed two-step process. The optimum temperature and inulinase concentration for SSF were 35°C and 0.25% (v/w, 4.4 units/g of sugar), respectively. In order to operate the SSF process in a continuous mode, inulinase and Z.mobilis cells were coimmobilized in alginate beads, using chitin as a matrix for enzyme immobilization. The maximum ethanol productivity of the continuous SSF process was 55.1 g/L/h, with 55% conversion yield. At the conversion yield of 90%, the productivity was 32.7 g/L/h. The continuous SSF system could be operated stably over 2 wk with an ethanol concentration of 48.6 g/L (95% of theoretical yield).