Fermentation Of Straw Research Articles

In situ laccase treatment enhances the fermentability of steam-exploded wheat straw in SSCF processes at high dry matter consistencies

This work evaluates the in situ detoxification of inhibitory lignocellulosic broths by laccases to facilitate their fermentation by the xylose-consuming Saccharomyces cerevisiae F12. Treatment of wheat straw slurries with laccases prior to SSCF processes decreased the total phenolic content by 50-80%, reducing the lag phase and increasing the cell viability. After laccase treatment, a negative impact on enzymatic hydrolysis was observed. This effect, together with the low enzymatic hydrolysis yields when increasing consistency, resulted in a decrease in final ethanol yields. Furthermore, when using high substrate loading (20% DM (w/v)), high concentration of inhibitors prevailed in broths and the absence of an extra nitrogen source led to a total cell growth inhibition within the first 24h in non-treated samples. This inhibition of growth at 20% DM (w/v) was overcome by laccase treatment with no addition of nitrogen, allowing S. cerevisiae F12 to produce more than 22 g/L of ethanol.

Optimisation of simultaneous saccharification and fermentation of wheat straw for ethanol production

With the goal of obtaining a high ethanol yield, wheat straw (WS) was pretreated with a 1.0% (w/w) NaOH solution. Further parameters, including temperature, enzyme loading, yeast concentration and pH that would affect the ethanol yield through simultaneous saccharification and fermentation (SSF), were optimised by means of Box-Behnken design (BBD), a response surface methodology (RSM). All of the experiments were carried out with an initial solid content of 16.0% (w/v) and fermentation time of 120h. A well fitted regression equation with an R2 value of 0.9603 was obtained. The predicted maximum response value (ethanol yield) was 69.49% under the optimised conditions for SSF: temperature of 37.5°C, enzyme loading of 30 FPU/g substrate, yeast concentration of 10g/L and pH of 4.6. The validation experimental result showed that the maximum ethanol yield was 70.76%, which was in accordance with the predicted value.

Production, Purification, and Characterization of Exoglucanase by Aspergillus fumigatus

Fungi are considered good producers of industrially valuable enzymes with higher enzymatic activities. Among these cellulases are group of extracellular enzymes commonly employed in many industries for the hydrolysis of cellulolytic material. Aspergillus fumigatus produced exoglucanase having high enzymatic activity (83 U/gds) during the solid-state fermentation of wheat straw under optimum physical and nutritional conditions. Maximum production was obtained after 72 h of fermentation, at 55 °C temperature, pH 5.5, 80 % moisture level, and 2 mL fungal inoculum. Production was further increased by the addition of fructose (0.3 %) as additional carbon source, peptone (0.4 %) as nitrogen source, Tween-80 (0.3 %) as surfactant, and ammonium sulfate (0.2 %) in media. Exoglucanase was 2.30-folds purified by adding 40 % ammonium sulfate with volumetric activity 95.4 U/gds and specific activity 14.74 U/mg. Further, it was 5.18-folds purified by gel filtration chromatography with volumetric activity 115.2 U/gds and specific activity 33.10 U/mg. Purified exoglucanase has maximum activity at 55 °C and pH 4.8 using 1 % Avicel aqueous solution as substrate. The K(m) and V(max) were 4.34 mM and 7.29 μM/min, respectively. Calcium, magnesium, and zinc ions have positive effect on exoglucanase activity.

Simultaneous Saccharification and Fermentation of Rice Straw Pretreated by a Sequence of Dilute Acid and Dilute Alkali at High Dry Matter Content

In lignocellulosic materials, the presence of lignin and hemicellulose makes the access of enzymes to cellulose difficult, thus reducing the efficiency of the hydrolysis. To improve the substrate hydrolysis for ethanol production, and to decrease the ethanol cost, rice straw was pretreated by a sequence of dilute acid and dilute alkali to remove lignin and hemicellulose, and then the production of bio-ethanol from the pretreated rice straw using simultaneous saccharification and fermentation at high dry content was investigated. After the complex pretreatment, the cellulose content in rice straw increased from 41.5 to 88.5%. Complex method and dilute acid pretreatment of rice straw result in glucose concentrations of 101.7 and 50.2 g/L, respectively. As a result, ethanol concentration of 58.7 g/L was obtained by simultaneous saccharification and fermentation of rice straw pretreated using a sequence of dilute acid and dilute alkali at a substrate concentration of 160 g/L; the ethanol yield was 73.4% based on the glucose content in the raw material. A biorefinery combining a sequence of dilute acid and dilute alkali pretreatment with commercial ethanol instant active dry yeast (S. cerevisiae) in SSF could achieve 175 g EtOH/kg untreated rice straw.

Effects of Branched-chain Amino Acids on In vitro Ruminal Fermentation of Wheat Straw.

This study investigates the effects of three branched-chain amino acids (BCAA; valine, leucine, and isoleucine) on the in vitro ruminal fermentation of wheat straw using batch cultures of mixed ruminal microorganisms. BCAA were added to the buffered ruminal fluid at a concentration of 0, 2, 4, 7, or 10 mmol/L. After 72 h of anaerobic incubation, pH, volatile fatty acids (VFA), and ammonia nitrogen (NH3-N) in the ruminal fluid were determined. Dry matter (DM) and neutral detergent fiber (NDF) degradability were calculated after determining the DM and NDF in the original material and in the residue after incubation. The addition of valine, leucine, or isoleucine increased the total VFA yields (p≤0.001). However, the total VFA yields did not increase with the increase of BCAA supplement level. Total branched-chain VFA yields linearly increased as the supplemental amount of BCAA increased (p<0.001). The molar proportions of acetate and propionate decreased, whereas that of butyrate increased with the addition of valine and isoleucine (p<0.05). Moreover, the proportions of propionate and butyrate decreased (p<0.01) with the addition of leucine. Meanwhile, the molar proportions of isobutyrate were increased and linearly decreased (p<0.001) by valine and leucine, respectively. The addition of leucine or isoleucine resulted in a linear (p<0.001) increase in the molar proportions of isovalerate. The degradability of NDF achieved the maximum when valine or isoleucine was added at 2 mmol/L. The results suggest that low concentrations of BCAA (2 mmol/L) allow more efficient regulation of ruminal fermentation in vitro, as indicated by higher VFA yield and NDF degradability. Therefore, the optimum initial dose of BCAA for in vitro ruminal fermentation is 2 mmol/L.

Effect of m&lt;sub&gt;C&lt;/sub&gt;/m&lt;sub&gt;N&lt;/sub&gt; on Acidification Characteristic of a New Complex Microbial Community LZF-12 with High Cellulose-Degradation Ability

The key rate-limiting step of methane production by dry anaerobic fermentation with straw as main materials is acidication phase, and carbon nitrogen ratio (mC/mN) is major factor in affecting microbial fermentation performance. In this study, a batch test was carried out to investigate the effect of different mC/mN ratio on acidogenic fermentation performance by means of a new medium-temperature complex microbial community LZF-12 with high efficent lignocellulosic degration, which straw and peptone were sole carbon and nitrogen respectively in reaction system. The results showed that flora growth of LZF-12 increased graduately along with the dicrease of mC/mN ratio, especially that the mC/mN ratio reached 5.0, the growth rate of microbial flora was obviously better than that of other mC/mN ratio, and pH revealed similar change trend that finial pH was between 6-7 along with different mC/mN ratio. Analysis of straw weightlessness revealed that substrate degradation rate achieved above 70% at the condition of diffenent mC/mN ratio, and fermentation was typically acetate-type, which main liquid end production were volatile fatty acid (VFA) comprising 90% acetate, butyate and a small amount of ethanol and propionate. This work presents important analysis of fermentation property together with carbon nitrogen scale applicable for biodegradation process of cellulose by complex microbial community LZF-12, and is benefical to technological optimization of dry anaerobic straw fermentation.

SSF of steam-pretreated wheat straw with the addition of saccharified or fermented wheat meal in integrated bioethanol production

BackgroundIntegration of second-generation (2G) bioethanol production with existing first-generation (1G) production may facilitate commercial production of ethanol from cellulosic material. Since 2G hydrolysates have a low sugar concentration and 1G streams often have to be diluted prior to fermentation, mixing of streams is beneficial. Improved ethanol concentrations in the 2G production process lowers energy demand in distillation, improves overall energy efficiency and thus lower production cost. There is also a potential to reach higher ethanol yields, which is required in economically feasible ethanol production. Integrated process scenarios with addition of saccharified wheat meal (SWM) or fermented wheat meal (FWM) were investigated in simultaneous saccharification and (co-)fermentation (SSF or SSCF) of steam-pretreated wheat straw, while the possibility of recovering the valuable protein-rich fibre residue from the wheat was also studied.ResultsThe addition of SWM to SSF of steam-pretreated wheat straw, using commercially used dried baker’s yeast, S. cerevisiae, resulted in ethanol concentrations of about 60 g/L, equivalent to ethanol yields of about 90% of the theoretical. The addition of FWM in batch mode SSF was toxic to baker’s yeast, due to the ethanol content of FWM, resulting in a very low yield and high accumulation of glucose. The addition of FWM in fed-batch mode still caused a slight accumulation of glucose, but the ethanol concentration was fairly high, 51.2 g/L, corresponding to an ethanol yield of 90%, based on the amount of glucose added.In batch mode of SSCF using the xylose-fermenting, genetically modified S. cerevisiae strain KE6-12, no improvement was observed in ethanol yield or concentration, compared with baker’s yeast, despite the increased xylose utilization, probably due to the considerable increase in glycerol production. A slight increase in xylose consumption was seen when glucose from SWM was fed at a low feed rate, after 48 hours, compared with batch SSCF. However, the ethanol yield and concentration remained in the same range as in batch mode.ConclusionEthanol concentrations of about 6% (w/v) were obtained, which will result in a significant reduction in the cost of downstream processing, compared with SSF of the lignocellulosic substrate alone. As an additional benefit, it is also possible to recover the protein-rich residue from the SWM in the process configurations presented, providing a valuable co-product.

Effect of inclusion of grasses and wet hulless-barley distillers’ grains on the fermentation and nutritive quality of oat straw- and straw-grass silages in Tibet

In order to enlarge the feed resources in Tibet, oat straw was conserved as silage by combining with tall fescue and wet hulless-barley distillers’ grains (WHDG). In Experiment 1, oat straw was ensiled with four levels of tall fescue (0, 20, 40 or 60% of fresh weight) in laboratory silos for 30 days. Ensiling oat straw with tall fescue significantly increased (P &lt; 0.05) lactic acid and water-soluble carbohydrate contents, and significantly (P &lt; 0.05) decreased acetic acid, propionic acid, butyric acid and total volatile fatty acid concentrations. The values of pH and ammonia/total N decreased with the increase in tall fescue ratios. There were no significant differences (P &gt; 0.05) in pH value between 40 and 60% tall fescue inclusion silages. To maximise the use of straw, it was suggested that 40% tall fescue inclusion was proper for further study. In Experiment 2, mixture of tall fescue and oat straw (6/4) were ensiled with 0, 10, 20 or 30% WHDG, triplicate silos for each treatment were opened on 7, 14, 30 and 60 days after ensiling, respectively, the fermentation characteristics and in vitro rumen degradability were analysed. WHDG addition significantly improved the fermentation quality of mixed silages, indicated by significantly lower (P &lt; 0.05) pH, ammonia/total N , butyric acid and propionic acid concentrations and significantly higher (P &lt; 0.05) DM and lactic acid content than the control. WHDG addition silages also showed higher crude protein contents, and lower neutral detergent fibre and acid detergent fibre content. These results suggest that adding WHDG to mixture of oat straw and tall fescue before ensiling appears to be a feasible strategy to improve the fermentation and nutritive quality of straw-grass silage.

Glucose and xylose co-fermentation of pretreated wheat straw using mutants of S. cerevisiae TMB3400

Wheat straw was pretreated and fermented to ethanol. Two strains, which had been mutated from the genetically modified Saccharomyces cerevisiae TMB3400, KE6-12 and KE6-13i, have been used in this study and the results of performance were compared to that of the original strain. The glucose and xylose co-fermentation ability was investigated in batch fermentation of steam-pretreated wheat straw (SPWS) liquid (undiluted, and diluted 1.5 and 2 times). Both strains showed improved xylose uptake in diluted SPWS liquid, and increased ethanol yields compared with the original TMB3400 strain, although xylitol formation also increased slightly. In undiluted SPWS liquid, however, only KE6-13i performed better than the original strain regarding xylose utilization.Fed-batch fermentation of 1.5 and 2 times diluted liquid was performed by adding the glucose-rich hydrolysates from enzymatic hydrolysis of the solid fraction of SPWS at a constant feed rate after 5h of fermentation, when the glucose had been depleted. The modified strains showed improved xylose conversion; however, the ethanol yield was not significantly improved due to increased glycerol production. Fed-batch fermentation resulted in faster xylose utilization than in the batch cases.

Variety effect on composition, kinetics of fermentation and &lt;i&gt;in vitro&lt;/i&gt; digestibility of oat (&lt;i&gt;Avena sativa&lt;/i&gt; L.) straw and its neutral detergent fibre

Yield, chemical composition, in vitro digestibility and kinetics of fermentation of straw from 18 varieties of oats (Avena sativa L.) were studied. All the straw varieties were grown in three replicates under the same agronomic conditions. Significance differences were observed in the yield of straw (4.4 to 7.5 ton dry matter (DM)/ha) from different varieties. The proportion of seed/straw from these varieties varied from 0.28 to 1.02. Crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) content varied from 24.2 to 48.1, 626 to 708, 437 to 533 and 52.0 to 92.4 g/kg DM, respectively in the straws. In vitro organic matter digestibility (IVOMD) differed among varieties and varied from 400 to 539 g/kg DM. The mean value of digestible organic matter yield (DOM) was 2.34 ton/ha. A significant difference was observed in the potential gas production (A) and lag time (L) among varieties. The fractional rate of gas production (c, /h) ranged from 0.030 to 0.034. The results emphasized that in any evaluation of oat varieties, kinetics of digestion or fermentation should be taken into consideration as well as yield and digestibility.

Effect of Temperature on Dry Anaerobic Fermentation of Animal Manure and Straw

Dry anaerobic fermentation of animal manure and straw was conducted to produce biogas. Under C/N=25-30 and TS=20%, three different temperature conditions of room temperature condition(16.5°C-25°C), mesophilic condition(36°C) and thermophilic condition(55°C) were tested to investigate the effect of operation temperature on dry fermentation. The results show that dry fermentation under room temperature starts up slowly with low biogas production, so room temperature is unfit for dry fermentation. Dry fermentation under thermophilic condition and mesophilic condition proceed steadily with high biogas production and mesophilic condition is more suitable for dry fermentation. The organic loading rates under thermophilic condition and mesophilic condition are 1.69 kg•m-3•d-1 and 1.89 kg•m-3•d-1 respectively with total solid (TS) biogas yields of 0.237 m3•kg-1 and 0.208 m3•kg-1, and volumetric biogas yields of 0.401 m3•m-3•d-1 and 0.393 m3•m-3•d-1 respectively. It could provide instructive meaning to the engineering application of dry anaerobic fermentation.

Feasibility of rice straw as alternate substrate for biobutanol production

Biobutanol has recently emerged as a potential alternate liquid fuel for gasoline and diesel. In this work, we have studied clostridial fermentation of stress assisted-acid hydrolyzed rice straw that exhibited a typical trend of acidogenesis followed by solventogenesis. Acid hydrolysis of 5% (w/v) mixture of rice straw in water with simultaneous application of shearing stress resulted in release of 3.9% (w/v) total sugar out of which 3.1% (w/v) was reducing sugar. Glucose formed major fraction (75%) of the reducing sugar (or 2.3% w/v total sugar). Thus, essentially, 5% (w/v) of rice straw solution released nearly 46% (w/w) (i.e. 23gL−1 glucose for 50gL−1 rice straw solution) glucose. Anaerobic fermentation of rice straw hydrolyzate using Clostridium acetobutylicum NCIM 2337 resulted in production of 6.24gL−1 of acetone, 13.5gL−1 of butanol and only 0.82gL−1 of ethanol. The net consumption of substrates was as follows: glucose 12.86gL−1 (i.e. ∼55%), total reducing sugar 18.32gL−1 (∼57%) and total sugar 24.5gL−1 (∼61%). Thus, higher solvents yield and significant sugar utilization makes rice straw a potential feedstock for biofuels production.

Fermentasi Jerami Padi Menggunakan White rot fungi dan Suplementasi Saccharomyces cerevisiae Pengaruhnya terhadap Kecernaan Nutrien Secara In Vitro

The influence of rice straw fermentation using white rot fungi and saccharomyces cerevisiae supplementation on in vitro nutrient digestibilityABSTRACT. An experiment to investigate the effect of rice straw fermented using white rot fungi and Saccharomyces cerevisiae supplementation on nutrient digestibility In Vitro had been implemented in two phases. The first experiments undertaken to make rice straw fermentation, using experimental methods with a Completely Randomized Design. As the treatment were White rot fungi (Phanerochaete chrysosporium) 0, 5 and 10 g/kg of rice straw (DM basis). Each treatment was repeated six times, so there are 18 experimental units. The variables measured included nutrient content of rice straw. A second experiment carried out in vitro to test the best rice straw fermentation results of the first experiment, using experimental methods, with a Completely Randomized Design. As the treatment were the supplementation of Saccharomyces cerevisiae (0, 2, 4% of the weight of fermented rice straw, DM basis). The variables measured included digestibility of dry matter, organic matter, cellulose and lignin digestibility of feed containing fermented straw. The data obtained were analyzed using analysis of variance test followed by Orthogonal Polynomials. The results can be concluded that the fermented rice straw using Phanerochaete chrysosporium 10 g/kg of rice straw is the best nutrient content. Saccharomyces cerevisiae supplementation on feed that contains fermented rice straw using Phanerochaete chrysosporium 10 g/kg rice straw is 2%.

Purification of xylitol produced from fermented wheat straw hydrolysate

Purification of xylitol produced from fermented wheat straw hydrolysate

One-step fermentation of pretreated rice straw producing microbial oil by a novel strain of Mortierella elongata PFY

A fungus strain producing microbial oils utilizing pretreated rice straw was isolated from soil. This strain was identified as Mortierella elongata PFY based on the morphology and internal transcribed spacer sequence. Using pretreated rice straw as substrate, the average yield of total lipids was 7.07% after 7days fermentation. The GC–MS detection demonstrated that the lipids were composed of saturated fatty acids and polyunsaturated fatty acids. This work presents one new way to make the waste biomass (rice straw) valuable.

Ethanol production by repeated-batch simultaneous saccharification and fermentation (SSF) of alkali-treated rice straw using immobilized Saccharomyces cerevisiae cells

Repeated-batch simultaneous saccharification and fermentation (SSF) of alkali-treated rice straw using immobilized yeast was developed to produce ethanol. Saccharomyces cerevisiae cells were immobilized by entrapping in photocrosslinkable resin beads, and we evaluated the possibility of its reuse and ethanol production ability. In batch SSF of 20% (w/w) rice straw, the ethanol yields based on the glucan content of the immobilized cells were slightly low (76.9% of the theoretical yield) compared to free cells (85.2% of the theoretical yield). In repeated-batch SSF of 20% (w/w) rice straw, stable ethanol production of approx. 38gL−1 and an ethanol yield of 84.7% were obtained. The immobilizing carrier could be reused without disintegration or any negative effect on ethanol production ability.

Effects of xylanase supplementation on ruminal digestibility in fistulated non-lactating dairy cows fed rice straw

The effect of xylanase product on ruminal disappearance and rumen fermentation of rice straw based diet was evaluated in fistulated non-lactating dairy cows. Three fistulated non-lactating dairy cows were used in 3×3 Latin squares design; the trial consisted of 3 periods of 21d in each period. Treatments were: (1) control, (2) 10g xylanase/cow/d, and (3) 20g xylanase/cow/d. The commercial xylanase enzyme (endo-1, 4-beta-xylanase, EC 3.2.1.8) which was a fibrolytic enzyme powder (Porzyme® 93010; Danisco Animal Nutrition) was used in this study. Diets offered as 3kg/d of concentrate containing 17% CP together with ad libitum rice straw and clean water. Enzyme did not change dry matter intake, ruminal pH and NH3–N concentrations. DM and ADF potential disappearance fraction, DM and ADF total disappearance were unaffected by the enzyme supplementation. However, NDF potential disappearance fraction, NDF total disappearance were increased when the enzyme was added at a high dose. Hemicellulose degradability in 0, 3, 6, 12, 24, 48, 72 and 96h were unaffected by supplementation of xylanase. Total volatile fatty acids concentration, molar proportion of acetate, propionate and butyrate and ratio of acetate: propionate at each hour of incubation were unaffected by xylanase.

Research on the White-Rot Fungi Degradation of Lignocellulose of Straw

The degradation law of straw lignin by white-rot fungi was studied. The adding amount of synthetic medium, the inoculum size and the temperature were investigated by experiment of single factor and orthogonal experiments. In the 6.5g straw fermentation medium, the optimum process conditions of degrading straw lignin by white-rot fungi were as follows: the adding amount of synthetic medium was 14mL; the inoculum size was 0.8mL; the temperature was 35°C. Through the additional experiment, degradation rate of the lignin was 49.50%; the degradation rates of cellulose and hemicellulose were 38.41% and 47.88%, respectively.

Measurement of process variables in solid-state fermentation of wheat straw using FT-NIR spectroscopy and synergy interval PLS algorithm

The feasibility of rapid determination of the process variables (i.e. pH and moisture content) in solid-state fermentation (SSF) of wheat straw using Fourier transform near infrared (FT-NIR) spectroscopy was studied. Synergy interval partial least squares (siPLS) algorithm was implemented to calibrate regression model. The number of PLS factors and the number of subintervals were optimized simultaneously by cross-validation. The performance of the prediction model was evaluated according to the root mean square error of cross-validation (RMSECV), the root mean square error of prediction (RMSEP) and the correlation coefficient (R). The measurement results of the optimal model were obtained as follows: RMSECV=0.0776, Rc=0.9777, RMSEP=0.0963, and Rp=0.9686 for pH model; RMSECV=1.3544% w/w, Rc=0.8871, RMSEP=1.4946% w/w, and Rp=0.8684 for moisture content model. Finally, compared with classic PLS and iPLS models, the siPLS model revealed its superior performance. The overall results demonstrate that FT-NIR spectroscopy combined with siPLS algorithm can be used to measure process variables in solid-state fermentation of wheat straw, and NIR spectroscopy technique has a potential to be utilized in SSF industry.

Rapid determination of pH in solid-state fermentation of wheat straw by FT-NIR spectroscopy and efficient wavelengths selection

In the work discussed in this paper we investigated the feasibility of determination of the pH of a fermented substrate in solid-state fermentation (SSF) of wheat straw. Fourier-transform near-infrared (FT-NIR) spectroscopy was combined with an appropriate multivariate method of analysis. A genetic algorithm and synergy interval partial least-squares (GA-siPLS) were used to select the efficient spectral subintervals and wavelengths by k-fold cross-validation during development of the model. The performance of the final model was evaluated by use of the root mean square error of cross-validation (RMSECV) and correlation coefficient (R (c)) for the calibration set, and verified by use of the root mean square error of prediction (RMSEP) and correlation coefficient (R (p)) for the validation set. The experimental results showed that the optimum GA-siPLS model was achieved by use of seven PLS factors, when four spectral subintervals were selected by siPLS and then 45 wavelength variables were chosen by use of the GA. The predicted precision of the best model obtained was: RMSECV = 0.0583, R (c) = 0.9878, RMSEP = 0.0779, and R (p) = 0.9779. Finally, the superior performance of the GA-siPLS model was demonstrated by comparison with four other PLS models. The overall results indicated that FT-NIR spectroscopy can be successfully used for measurement of pH in solid-state fermentation, and use of the GA-siPLS algorithm is the best means of calibration of the model.