Continuous enzymatic cooking and liquefaction of starch using the technique of direct resistive heating

Continuous cooker prototypes of very simple design, using electricity as a primary energy source, were developed for the process of cooking and liquefaction of starch suspensions. Previous work on equipment using microwave dielectric heating has already been reported. Results of energy consumption as low as 330 kcal/kg based on starch content were achieved. Considering these results and looking for new solutions or engineering concepts, the authors have been investigating the possibility of using electric energy at 60 Hz for direct resistive heating, in which the starch suspension is the proper "resistor."The most important results of energetic yield obtained until now, working in a continuous process of cooking-liquefaction, are not larger than 235 kcal (272 Wh)/kg based on starch content. These results were obtained using a commercial grade alpha-amylase from B. subtillis, working with temperatures ranging from 70 to 75 degrees C, and with residence times in the reactor not greater than 1.5 min. The experiments of saccharification and fermentation accomplished as a test for the efficiency of this heating technique gave good results (as with a conventional technique) and thus enabled us to proceed with the studies.     

Continuous simultaneous saccharification and fermentation of starch using Zymomonas mobilis

A continuous process involving simultaneous saccharification and fermentation of liquefied starch has been developed using Zymomonas mobilis. Amyloglucosidase retention and cell recycle have been effected by using an Amicon hollow-fiber membrane system with a MW cutoff of 5000. Relatively high productivities of up to 60 g L(-1) h(-1) have been achieved at ethanol concentrations of 60-65 g/L. The system also offers the potential for reduced enzyme requirements for saccharification.     

Kinetics of enzymatic starch liquefaction: Simulation of the high-molecular-weight product distribution

Enzymatic corn starch liquefaction with alpha-amylase was carried out. Molecular weight distributions of the resulting hydrolysates are presented using aqueous size exclusion chromatographic techniques. It is demonstrated that despite the fact that the enzyme employed reacts in a random endoacting manner, the product distributions are nonrandom. The results are explained in part by a multimerization process whereby the polymeric substrate molecules preferentially associate, forming intermolecular aggregates. These aggregates are either a consequence of the manner in which the material is deposited into the native granular structure of starch or due to intrinsic physical chemical properties of the polysaccharide. In the latter case, the results are shown to correspond to known multimerized amylose, although complete characterization of the polysaccharide is currently not available. The results presented are used to develop a simplified kinetic model of starch liquefaction and shown to simulate the product distributions accurately.     

Simultaneous enzymatic wheat starch saccharification and fermentation to lactic acid by Lactococcus lactis

Simultaneous saccharification of starch from whole-wheat flour and fermentation to lactic acid (SSF) was investigated. For saccharification the commercial enzyme mixture SAN Super 240 L, having α-amylase, amyloglucosidase and protease activity, was used, and Lactococcus lactis ssp. lactis ATCC 19435 was used for the fermentation. SSF was studied at flour concentrations corresponding to starch concentrations of 90 g/l and 180 g/l and SAN Super concentrations between 3 μl/g and 8 μl/g starch. Kinetic models, developed for the saccharification and fermentation, respectively, were used for simulation and data from SSF experiments were used for model verification. The model simulated SSF when sufficient amounts of nutrients were available during fermentation. This was achieved with high wheat flour concentrations or with addition of yeast extract or amino acids. Nutrient release was dependent on the level of enzyme activity. Received: 26 January 1999 / Accepted: 20 February 1999     

Simultaneous saccharification and fermentation of broken rice: an enzymatic extrusion liquefaction pretreatment for Chinese rice wine production

Broken rice, pretreated by enzymatic extrusion liquefaction, was used to produce Chinese rice wine by simultaneous saccharification and fermentation (SSF) process in this study. The study compared the novel process and traditional process for Chinese rice wine fermentation utilizing broken rice and head rice, respectively. With the optimum extrusion parameters (barrel temperature, 98 °C; moisture content, 42 % and amylase concentration, 1 ‰), 18 % (v/v at 20 °C) alcoholic degree, 37.66 % fermentation recovery and 93.63 % fermentation efficiency were achieved, indicating enzymatic extrusion-processed rice wine from broken rice exhibited much higher fermentation rate and efficiency than traditional-processed rice wine from head rice during SSF. The starch molecule distribution data indicated that the alcoholic degree was related to the oligosaccharides’ formation during enzymatic extrusion. Sum of amino acid (AA) in the extrusion-processed wine was 53.7 % higher than that in the traditional one. These results suggest that the enzymatic extrusion pretreatment for broken rice is a feasible and alternative process in the fermentation of Chinese rice wine.     

Ultrasound effect on enzymatic saccharification

Summary An ultrasound field during enzymatic saccharification ehanced the rate and extent of reaction of sugarcane bagasse that had been previously pretreated inducing a matrix swelling and partial delignification.     

Continuous enzymatic saccharification of cellulose with culture filtrates of trichoderma viride QM 6a.

Continuous saccharification of Solka Floc (cellulose pulp) in single and four-vessel stirred-tank reactor systems has been possible employing enzymes obtained directly from submerged fermentation of Trichoderma viride QM 6a. Studies on the effect of modification of the solid substrate, enzyme stability, substrate concentration, and the influence of reducing sugar concentration on the rate of hydrolysis are reported. While susceptibility of substrate to digestion is not affected by heating alone, it is strikingly increased by heating plus grinding, or by grinding following heating. Batch and steady state continuous saccharification experiments have yielded more than 5% reducing sugar in the effluent with a dilution rate of 0.025 hr^?1 at 50°C, at a substrate level of 10%. An average glucose concentration of 3.4% has been obtained in the effluent of a continuous saccharification using 5% substrate at the same dilution rate and temperature.     

Efficiency of pretreatments for optimal enzymatic saccharification of soybean fiber

The effectiveness of several pretreatments [high-power ultrasound, sulfuric acid (H₂SO₄), sodium hydroxide (NaOH), and ammonium hydroxide (NH₃OH)] to enhance glucose production from insoluble fractions recovered from enzyme-assisted aqueous extraction processing of extruded full-fat soybean flakes (FFSF) was investigated. Sonication of the insoluble fraction at 144 μm_{pp (peak-to-peak)} for 30 and 60 s did not improve the saccharification yield. The solid fractions recovered after pretreatment with H₂SO₄ [1% (w/w), 90 °C, 1.5 h], NaOH [15% (w/w), 65 °C, 17 h], and NH₃OH [15% (w/w), 65 °C, 17 h] showed significant lignin degradation, i.e., 81.9%, 71.2%, and 75.4%, respectively, when compared to the control (7.4%). NH₃OH pretreatment resulted in the highest saccharification yield (63%) after 48 h of enzymatic saccharification. A treatment combining the extraction and saccharification steps and applied directly to the extruded FFSF, where oil extraction yield and saccharification yield reached 98% and 43%, respectively, was identified.     

Effects of agitation on enzymatic saccharification of cellulose

Summary Crystalline cellulose Avicel has been hydrolyzed byTrichoderma viride cellulase (Meicelase CEPB) under vaned agitation conditions and the effect of agitation on the adsorption of cellulase on cellulose has been studied. Agitation was found to enhance the hydrolysis pf crystalline cellulose; possibly the agitation enhances the adsorption of exoglucanase to shift the adsorption balance of exoglucanase and endoglucanase to a direction favorable for their synergistic action on the surface of cellulose.     

Improvement and estimation of enzymic starch saccharification process

Summary The effect on the dextrose equivalent value (DE) obtained in maltodextrin saccharification with a glucoamylase preparation containing various quantities of acid stable -amylase isolated by anion exchange chromatography was investigated. When the acid stable -amylase activity was increased 2.5-fold, a maximum DE value of 95.6% (glucose content, DX, 95.0%) was reached in 48 h, 1.4 % (DX of 1.1%) higher than that of the control (DE 94.2%; DX 93.9%).     

Laboratory-scale method for enzymatic saccharification of lignocellulosic biomass at high-solids loadings

Background  

Screening new lignocellulosic biomass pretreatments and advanced enzyme systems at process relevant conditions is a key factor in the development of economically viable lignocellulosic ethanol. Shake flasks, the reaction vessel commonly used for screening enzymatic saccharifications of cellulosic biomass, do not provide adequate mixing at high-solids concentrations when shaking is not supplemented with hand mixing.     

Simultaneous saccharification and fermentation of cellulose: effect of ethanol on enzymatic saccharification of cellulose

It was confirmed that simultaneous saccharification and fermentation are effective for accelerating enzymatic saccharification of cellulose. In this work, the effects of ethanol on the saccharification of tissue paper by Trichoderma cellulase (Meicelase CEPB) have been investigated. The following results were obtained. (1) Saccharification was inhibited by at least 0.2M ethanol. (2) Less than 4M ethanol did not affect the enzymatic activities of beta-glucosidase and endoglucanase (C(x)) at all. The thermal stability of endoglucanase was not also varied by ethanol. (3) It is suggested that ethanol depresses the adsorption of exoglucanase on cellulose. (4) The rate expression of saccharification of cellulose in the presense of ethanol is proposed. (5) The inhibititory effect of ethanol was found to become more significant in the later stages of the reaction than just the initial stage.     

Extracellular amylase production bySaccharomycopsis capsularis and its evaluation for starch saccharification

A strain of starch-assimilating yeast,Saccharomycopsis capsularis, isolated from Indian cereal-based fermented foods, produced significant levels of extracellular α-amylase and glucoamylase. The enzymes reached their peak activities during the stationary phase at the end of the 5th and 4th day of cultivation, respectively. The amylase yields were maximized by a proper choice of carbon and nitrogen sources, starting pH of the culture medium and growth temperature. High activities of the enzymes were obtained through inexpensive agricultural commodities, such as wheat bran and corn meal as carbon sources, and defatted soybean meal and peanut meal as nitrogen sources. A temperature of 28–32°C and an initial pH of 4.5–5.0 were optimum. The crude amylase mixture could liquefy and saccharify a 1% starch solution completely in 24 h at 50°C.     

Effects of growth stage on enzymatic saccharification and simultaneous saccharification and fermentation of bamboo shoots for bioethanol production

Bamboo is a fast-growing renewable biomass that is widely distributed in Asia. Although bamboo is recognised as a useful resource, its utilization is limited and further development is required. Immature bamboo shoots harvested before branch spread were found to be a good biomass resource to achieve a high saccharification yield. The saccharification yield of the shoots increased (up to 98% for immature Phyllostachys bambusoides) when xylanase was used in addition to cellulase. Simultaneous saccharification and fermentation (SSF) processing converted immature shoots of P. bambusoides and Phyllostachys pubescens to ethanol with an ethanol yield of 169 and 139 g kg⁻¹, respectively (98% and 81%, respectively, of the theoretical yields based on hexose conversion) when 12 FPU g⁻¹ enzyme and the yeast Saccharomyces cerevisiae were used.     

Simultaneous saccharification of cassava starch and fermentation of algae for biodiesel production

A simpler approach to produce biodiesel from cassava starch was established, which successfully integrates the simultaneous saccharification and heterotrophic algal fermentation in an identical system. Batch experiments were investigated to verify the feasibility of raw starchy substrates fermentation for microalgal oil. The highest cell density (49.34 g L⁻¹) and oil content (54.60%) were obtained in 5-L fed-batch cultivation via simultaneous saccharification and fermentation (SSF). It is demonstrated that the previous multistep hydrolysis and fermentation for feedstock oil could be replaced by SSF with higher energy efficiency and lower facility costs.     

Enhanced enzymatic saccharification of rice straw by microwave pretreatment

In this study, Box-Behnken design and response surface methodology were employed to plan experiments and optimize the microwave pretreatment of rice straw. Experimental results show that microwave intensity (MI), irradiation time (IT) and substrate concentration (SC) were main factors governing the enzymatic saccharification of rice straw. The maximal efficiencies of cellulose, hemicellulose and total saccharification were respectively increased by 30.6%, 43.3% and 30.3% under the optimal conditions of MI 680 W, IT 24 min and SC 75 g/L. The chemical composition analysis of straw further confirmed that microwave pretreatment could disrupt the silicified waxy surface, break down the lignin-hemicellulose complex and partially remove silicon and lignin.     

Cationic polyacrylamides enhance rates of starch and cellulose saccharification

Adding a cationic polyacrylamide (c-PAM) to either the amylase mediated hydrolysis of corn starch or the hydrolysis of wood fiber by cellulase can enhance the initial hydrolysis rates, although a rate decrease can occur under some conditions. Several c-PAMs can serve as catalysts and the same c-PAM can improve the efficiency of both amylase and cellulase. The initial amylase rate approximately doubles; the analogous cellulase hydrolysis rate increases by about 40%. c-PAMs increase the binding of enzyme to substrate.     

Characterization of enzymatic saccharification for acid-pretreated lignocellulosic materials with different lignin composition

The enzymatic saccharification of three different feedstocks, rice straw, bagasse and silvergrass, which had been pretreated with different dilute acid concentrations, was studied to verify how enzymatic saccharification was affected by the lignin composition of the raw materials. There was a quantitatively inverse correlation between lignin content and enzymatic digestibility after pretreatment with 1%, 2% and 4% sulfuric acid. The lignin accounted for about 18.8–21.8% of pretreated rice straw, which was less than the 23.1–26.5% of pretreated bagasse and the 21.5–24.1% of pretreated silvergrass. The maximum glucose yield achieved, under an enzyme loading 6.5 FPU g^?1 DM for 72 h, was close to 0.8 g glucose/g glucan from the enzymatic hydrolysis of the pretreated rice straw; this was twice that from bagasse and silvergrass. A decrease in initial rate of glucose production was observed in all cases when the raw materials underwent enzymatic saccharification with 4% sulfuric acid pretreatment. It is suggested that the higher acid concentration led to an inhibition of β-glucosidase activity. Fourier transform infrared (FTIR) spectroscopy further indicated the chemical properties of the rice straw and silvergrass become more hydrophilic after pretreatment using 2% of sulfuric acid, but the pretreated bagasse tended to become more hydrophobic. The hydrophilic nature of the pretreated solid residues may increase the inhibitive effects of lignin on the cellulase and this could become very important for raw materials such as silvergrass that contain more lignin.     

Application of cellulase and pectinase from fungal origin for the liquefaction and saccharification of biomass

Commercial cellulase [see 1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4] from Trichoderma viride and pectinase [poly(1,4-α-d-galacturonide) glycanohydrolase, EC 3.2.1.15] from Aspergillus niger have been applied to produce fermentation syrups from sugar-beet pulp and potato fibre. Cellulosic, hemicellulosic and pectic polysaccharides of these substrates were hydrolysed extensively. Recovery of enzymes has been investigated in a packed-column reactor, connected with a hollow-fibre ultrafiltration unit. Enzymes appeared to be stable in this type of reactor, although part of the enzyme activity was lost, especially by adsorption onto the substrate residue.