Investigates of substrate mingling ratio and organic loading rate of KOH pretreated corn stover and pig manure in batch and semi-continuous system:Anaerobic digestion performance and microbial characteristics

The effects of substrate mingling ratio(SMR)(1:1,1:2,1:3,3:1,and 2:1)and organic loading rate(OLR)(50-90 g total solids per liter per day)on anaerobic co-digestion performance and microbial characteristics were investigated for pig manure(PM)and pretreated/untreated corn stover in batch and semicontinuous anaerobic digestion(AD)system.The results showed that SMR and pretreatment affected co-digestion performance.The maximum cumulative methane yield of 428.5 ml·g^(-1)(based on volatile solids(VS))was obtained for PCP13,which was 35.7%and 40.0%higher than that of CSU and PM.In the first 5 days,the maximum methane yield improvement rate was 378.1%for PCP13.The daily methane yield per gram VS of PCP13 was 11.4%-18.5%higher than that of PC_(U)13.Clostridium_sensu_stricto_1,DMER64,and Bacteroides and Methanosaeta,Methanobacterium,and Methanospirillum had higher relative abundance at the genus level.Therefore,SMR and OLR are important factor affecting the AD process,and OLR can affect methane production through volatile fatty acids.

Effect of Application of a Bacteria Inoculant and Wheat Bran on Fermentation Quality of Peanut Vine Ensiled Alone or with Corn Stover

To find an effective method for ensiling peanut vine （PV）, fermentation characteristics and nutritional values of PV silage and the mixture of PV with corn stover （CS） silage in a ratio of 1 ： 1 fresh weight, prepared by adding lactic acid bacteria （LAB）, 10% wheat bran （WB） and LAB＋WB at ensiling were evaluated in 2009 and 2010. The fermentation qualities of PV silage ensiled with the LAB and WB additives were improved compared with those of the control （PV ensiled alone）. However, the pH did not decline to the critical level of 4.2, and the nutritional values of the silage were not protected against losses in the LAB and WB addition silages. Ensiling PV in mixture with CS generated optimal moisture content and buffering capacity （BC） of ensiled materials. After adding the LAB and WB additives to mixture silage, especially adding LAB＋WB, the fermentation qualities and nutritional values of the mixture silage were improved significantly （P〈0.05）, and the Flieg＇s score reached to 99. The result suggested that it is a feasible method to ensile the mixed materials of PV with CS by adding LAB and high concentration of water soluble-carbohydrate materials for providing a good fermentation quality of PV silage.

The effect of lactic acid bacteria inoculums on in vitro rumen fermentation, methane production, ruminal cellulolytic bacteria populations and cellulase activities of corn stover silage

The objective of this study was to investigate the effect of lactic acid bacteria(LAB) inoculums on fermentation quality and in vitro digestibility of corn stover silage.Corn stover was ensiled without(control) or with Lactobacillus plantarum(LP),Enterococcus faecalis(EF),and Enterococcus mundtii(EM) for 45 days.The fermentation characteristics were assessed,and subsequent in vitro dry matter digestibility(DM-D),neutral detergent fiber digestibility(NDF-D),volatile fatty acids(VFA),methane(CH4) production,cellulolytic bacteria proportions and their activities per corn stover silage were also determined.There was no significant difference(P>0.05) among the silage pH,lactic acid,crude protein(CP),water soluble carbohydrates(WSC) and lignocelluloses contents of different treatments.The relative proportions of Ruminococcus flavefaciens and Fibrobacter succinogenes,carboxymethyl-ocellulose and β-glycosidase activities,DM-D,NDF-D,and VFA production of in vitro incubation was higher(P<0.05) for silages inoculated with LP and EF than those of the control silage.Silage inoculated with LP showed the lowest(P<0.05) CH4 production per unit yield of VFA,which was positively corresponded to the lowest(P<0.05) ratio of acetate to propionate.In summary,the ensiling fermentation quality and subsequent utilization of corn stover silage were efficiently improved by inoculated with L.plantarum.

Comparison of forage yield,silage fermentative quality,anthocyanin stability,antioxidant activity,and in vitro rumen fermentation of anthocyanin-rich purple corn(Zea mays L.) stover and sticky corn stover

The objective of this study was to observe the forage yield, silage fermentative quality, anthocyanin stability, and antioxidant activity during the storage period and in vitro rumen fermentation of anthocyanin-rich purple corn （Zea mays L.） stover （PS） and sticky corn stover （SS）. Forage yield of corn stover was weighed and ensiled with two treatments： （1） hybrid sticky waxy corn stover （control）, and （2） hybrid purple waxy corn stover （treatment）. Samples were stored in mini-silos for periods of 0, 7, 14, 21,42, 63, 84, and 105 d. The results showed that PS had significantly higher （P〈0.05） yields of dry matter （DM）, organic matter （OM）, gross energy （GE）, crude protein （CP）, neutral detergent fiber （NDF）, acid detergent fiber （ADF）, and total anthocyanins than that of the SS. Anthocyanin-rich purple corn stover silage （PSS） showed higher （P〈0.05） levels of DM and CP relative to the sticky corn stover silage （SSS）. Although anthocyanin-rich PSS displayed a lower （P〈0.05） level of pelargonidin-3-glucoside （P3G）, it had higher （P〈0.05） levels of peonidin （Peo） and pelargonidin （Pel） compared to the control. Delphinidin （Del） and malvidin （Mal） were not detected in SSS during the ensilage period; in PSS, Del was no longer detected after 7 d of ensilage. Specifically, total anthocyanins in anthocyanin-rich PSS decreased rapidly （P〈0.05） prior to 7 d of ensilage, and then remained at relatively stable （P〉0.05） constants. Compared to the anthocyanin-rich PSS, SSS displayed significantly higher （P〈0.05） pH value and ammonia nitrogen （NH3-N） content. Propionic acid （PA） at 0 d and butyric acid （BA） during the entire study period were not detected, whereas anthocyanin-rich PSS showed a higher （P〈0.05） level of lactic acid （LA） than that of the SSS. Compared with the SSS extract, anthocyanin-rich PSS extract showed a higher （P〈0.05） level of 2,2-diphenyl-1-picryihydrazyl （DPPH） scavenging activity and displayed a lower （P〈0.05） half maximal inhibitory concentration （IC50） value. Moreover, anthocyanin-rich PSS reduced （P〈0.05） gas production （GP）, and displayed lower levels of immediately soluble fraction and ratio of acetic acid （AA） to PA at 12 h, but the other parameters were unaffected （P〉0.05） relative to the control. Taken together, the results indicated that： （1） anthocyanins could be stable in silage; （2） anthocyanin-rich PSS showed better silage fermentative quality and stronger antioxidant activity; and （3） anthocyanin-rich PSS had no negative effect on rumen fermentation parameters.

Pretreatment of Corn Stover Using Supercritical CO2 with Water-Ethanol as Co-solvent

Supercritical carbon dioxide,with water-ethanol as co-solvent,was applied to pretreat corn stover to enhance its enzymatic hydrolysis.The efficiency of pretreatment was evaluated by the final reducing sugar yield obtained from the enzymatic hydrolysis of cellulose.Under the operation conditions of pretreatment pressure 15 MPa,temperature 180 ℃ and time 1 h,the optimal sugar yield of 77.8℅ was obtained.Scanning electron microscopy(SEM) and chemical composition analysis were applied to the pretreated corn stover.The results showed that the surface morphology and microscopic structure of pretreated corn stover were greatly changed.After the pretreatment,the contents of hemicellulose and lignin were reduced obviously.Thus more cellulose was exposed,increasing the sugar yield.

Characterization of Lignins Isolated from Alkali Treated Prehydrolysate of Corn Stover

Lignins were isolated and purified from alkali treated prehydrolysate of corn stover. The paper presents the structural features of lignins in a series purification processes. Fourier transform infrared spectroscopy, ultraviolet-vis spectroscopy and proton nuclear magnetic resonance spectroscopy were used to analyze the chemical structure. Thermogravimetric analysis was applied to follow the thermal degradation, and wet chemical method was used to determine the sugar content. The results showed that the crude lignin from the prehydrolysate of corn stover was a heterogeneous material of syringyl, guaiacyl and p-hydroxyphenyl units, containing associated polysaccharides, lipids, and melted salts. Some of the crude lignin was chemically linked to hemicelluloses （mainly xylan）. The lipids in crude lignin were probably composed of saturated and/or unsaturated long carbon chains, fatty acids, tdterpenols, waxes, and derivatives of aromatic. The sugar content of purified lignin was less than 2.11%, mainly composed of guaiacyl units. DTGmax of purified lignin was 359 ℃. The majority of the hydroxyl groups were phenolic hydroxyl groups. The main type of linkages in purified lignin was β-O-4. Other types of linkages included β-5, β-β and α-O-4.

Effects of the dietary nonfiber carbohydrate content on lactation performance, rumen fermentation, and nitrogen utilization in mid-lactation dairy cows receiving corn stover

Background: Corn stover(CS) is an abundant source of feed for livestock in China. However, it is low in nutritional value that we have been seeking technologies to improve. Previous studies show that non-fiber carbohydrate(NFC)might limit the utilization of a CS diet by lactating dairy cows. Thus, this study was conducted to investigate the lactation performance and rumen fermentation characteristics in lactating cows consuming CS with two contents of NFC compared to an alfalfa hay-containing diet. Twelve Holstein cows were used in a replicated 3 × 3 Latin square design with three dietary treatments:(1) low-NFC diet(NFC = 35.6%, L-NFC),(2) high-NFC diet(NFC = 40.1%,H-NFC), and(3) alfalfa hay diet(NFC = 38.9%, AH).Results: Intake of DM was lower for cows fed H-NFC compared to L-NFC and AH, while the milk yield was higher in AH than in H-NFC and L-NFC(P < 0.01). The feed efficiency(milk yield/DM intake, 1.15 vs. 1.08, P < 0.01) were greater for cows fed H-NFC than L-NFC. The contents of milk protein and lactose were not different among the groups(P > 0.11), but milk fat content was higher for cows fed H-NFC and L-NFC compared to AH(P < 0.01). The rumen ammonia nitrogen concentration and the concentrations of urea nitrogen in blood and milk were lower for cows fed H-NFC and AH compared to L-NFC(P < 0.05). The concentrations of rumen propionate and total volatile fatty acids were different among groups(P < 0.05) with higher concentration for cows fed AH compared to H-NFC and L-NFC, and acetate concentration tended to be different among groups(P = 0.06).Conclusions: From the results obtained in this study, it was inferred that the increased NFC content in a diet containing corn stover can improve the feed efficiency and benefit the nitrogen conversion.

Yield and quality of maize stover: Variation among cultivars and effects of N fertilization

Biomass yields and concentrations of crude protein（CP）, ether extract（EE）, neutral detergent fiber（NDF）, acid detergent fiber（ADF）, and crude fiber（CF） were analyzed for five cultivars of summer-sown maize（Zea mays L.） stover grown in field trials at three rates of N fertilization, and sampled immediately after grain harvest.The results revealed differences in yields and concentrations of nutrients according to stalk height and hence harvest portion among the cultivars.N application greatly increased biomass yield and CP, especially in upper stalks and to a lesser extent, EE.Concentrations of NDF and ADF decreased as N rate increased.The results show that stovers from all local popular maize cultivars are suitable as animal fodder and that moderate N application improves feed quality of stover.

Effect on anaerobic digestion performance of corn stover by freezing–thawing with ammonia pretreatment

In order to enhance the biomethane production from corn stover, choosing effective pretreatment is one of the necessary steps before starting anaerobic digestion(AD).This study was aimed to analyze the effectiveness of freezing–thawing with ammonia pretreatment on substance degradation and AD performance of corn stover.Three ammonia concentrations(2%, 4%, and 6%) with two different moisture contents(50% and 70%) were used to pretreat the corn stover at two temperatures(-20 ℃ and 20 ℃).The result showed that an optimum pretreatment condition for corn stover was at the temperature of -20 ℃, moisture content of 70% and ammonia concentration of 2%.Under the optimum pretreatment condition, the maximum biomethane yield reached 261 ml·(g VS)^(-1), which was 41.08% higher than that of the untreated.Under different pretreatment conditions,the highest loss of lignin at -20 ℃ with 2% ammonia concentration was 63.36% compared with the untreated.The buffer capacity of AD system was also improved after the freezing–thawing with ammonia pretreatment.Therefore, the freezing–thawing with ammonia pretreatment can be used to improve AD performance for corn stover.This study provides further insight for exploring an efficient freezing–thawing with ammonia pretreatment strategy to enhance AD performance for the practical application.

Efficient and Comprehensive Utilizatio℃n of Hemicellulose in the Corn Stover

Pretreatment of the corn stover powder by dilute sulphuric acid （solid-liquid ratio 1 ： 20） at 130 for 30 min was carried out with 89.09% of the hemicellulose removed. After filtration, the xylose-rich corn stover pretreatment liquid, whose fermentable sugar was from hemicellulose hydrolysis only, consisting of 81.16% xylose and 15.27% glucose, was used to cultivate genetic recombinant Escherichia coli BL21 with human-like collagen （HLC） expression enhanced by 50.00% and 63.71% xylose consumption.

Ignition and Emission Characteristics of Ignition-assisting Agents for Densified Corn Stover Briquette Fuel

Ignition-assisting agents for densified corn stover briquette fuel(DCBF) were developed,and their ignition and emission characteristics were investigated using type LLA-6 household cooking stove.Three waste liquid fuels,waste engine oil(E) ,diesel oil(D) ,and industrial alcohol(A) ,were used as raw materials to make 25 ignitionassisting agents by mixing at different ratios.Their ignition performance was evaluated in terms of ignition time and cost.It was found that ignition-assisting agents ED15(a mix of E and D at volume ratio of 1︰5) and DA51(a mix of D and A at volume ratio of 5︰1) presented better ignition results with shorter ignition time(40-53 s) and lower cost(6.1 and 5.3 cents) at the dosages of 9 ml and 8 ml,respectively.The emission of O2,CO,CO2,NOx,and SO2,the temperature in fume gas,and combustion efficiency were investigated for ED15 and DA51.The results show that the emission of ED15 with the dosage of 9 ml is lower than that of DA51 with the dosage of 8 ml in the ignition process.ED15 at the dosage of 9 ml achieves satisfactory combustion efficiency and emits less pollutant,so it is recommended for practical application.The study will provide a cost-effective and environmentally friendly approach to fast ignite DCBF and break the barrier to the practical application of DCBF.

Screening of a microbial consortium with efficient corn stover degradation ability at low temperature

To speed up the degradation of corn stover directly returned to soil at low temperature, the corn stover-degrading microbial consortium GF-20, acclimated to biological decomposition in the frigid region, was successfully constructed under a long-term limiting substrate. To evaluate its potential in accelerating the decomposition of un-pretreated corn stover, the decomposing property, fermentation dynamic and the microbial diversity were analyzed. GF-20 degraded corn stover by 32% after 15-day fermentation at 10℃. Peak activities of filter paperlyase（FPA）, β-glucosidases（CB）, endoglucanases（Cx）, and cellobiohydrolases（C1） were 1.15, 1.67, 1.73, and 1.42 U m L^–1, appearing at the 6th, 3rd, 11 th, and 9th d, respectively. The p H averaged at 6.73–8.42, and the optical density（OD） value peaked at 1.87 at the 120 h of the degradation process. Cellulase, hemicellulase and lignin in corn stover were persistently degraded by 44.85, 43.85 and 25.29% at the end of incubation. Result of denaturing gradient gel electrophoresis（DGGE） profiles demonstrated that GF-20 had a stable component structure under switching the temperature and p H. The composition of the GF-20 was also analyzed by constructing bacterial 16 S r DNA clone library and fungal 18 Sr DNA-PCR-DGGE. Twenty-two bacterial clones and four fungal bands were detected and identified dominant bacteria represented by Cellvibrio mixtus subsp., Azospira oryzae, Arcobacter defluyii, and Clostridium populeti and the fungi were mainly identified as related to Trichosporon sp.

Effects of Corn Stover Incorporated in Dry Farmland on Soil Fertility

Seven years' field experiments on application of corn stover and/or cattle manure combined with chemical fertilizers were carried out in Shouyang Dryland Farming Experimental Station. Results showed that the increased available N in the plough layer was mainly influenced by the application of cattle manure; the available P was mainly influenced by the application of chemical fertilizer; the available K was mainly influenced by the incorporation of corn stover. The organic matter contents in the soils treated with corn stover or cattle manure were kept in balance under the experimental conditions. Corn yield and water use efficiency were influenced significantly not only by fertilizer N but also by incorporated corn stover. The results suggested that the highest N uptake, yield and water use efficiency could be obtained at rates of 105 kg fertilizer N, 6000 kg corn stover, and 1500 kg cattle manure per hectare. The experiments supplied information on nutrient recycling and use of corn stover as sources of fodder and organic fertilizer for balancing application of organic and inorganic fertilizer, improving soil fertility and increasing crop yield with incorporation of corn stover in soil.

Efficient microwave-assisted production of biofuel ethyl levulinate from corn stover in ethanol medium

Levulinate esters are versatile chemicals that have been used in various fields. Herein, the production of ethyl levulinate（EL） from corn stover was investigated under microwave irradiation. Several reaction parameters, including acid concentration, reaction temperature, reaction time, and liquid-to-solid mass ratio, were investigated to evaluate the reaction conditions. Response surface methodology（RSM） was employed to optimize the reaction conditions for the production of EL. A quadratic polynomial model was fitted to the data with an R2 value of 0.93. The model validation results reflected a good fit between the experimental and predicted values. A high conversion yield（58.1 mol%） was obtained at the optimum conditions of 190℃, 30.4 min, 2.84 wt% acid, and 15 g/g liquid-to-solid mass ratio. Compared with conventional heating, microwave irradiation facilitated the conversion of corn stover to EL by dramatically shortening the reaction time from several hours to ～30 min. Thus, microwave-assisted conversion of corn stover to EL is an efficient way of utilizing a renewable biomass resource.

Comprehensive Evaluation and Prediction of the Effectiveness of H_(2)O_(2)- assisted Na_(2)CO_(3)Pretreatment of Corn Stover Using Multivariate Analysis

In this study,multivariate analysis methods,including a principal component analysis(PCA)and partial least square(PLS)analysis,were applied to reveal the inner relationship of the key variables in the process of H_(2)O_(2)-assisted Na_(2)CO_(3)(HSC)pretreatment of corn stover.A total of 120 pretreatment experiments were implemented at the lab scale under different conditions by varying the particle size of the corn stover and process variables.The results showed that the Na_(2)CO_(3) dosage and pretreatment temperature had a strong influence on lignin removal,whereas pulp refining instrument(PFI)refining and Na_(2)CO_(3) dosage played positive roles in the final total sugar yield.Furthermore,it was found that pretreatment conditions had a more significant impact on the amelioration of pretreatment effectiveness compared with the properties of raw corn stover.In addition,a prediction of the effectiveness of the corn stover HSC pretreatment based on a PLS analysis was conducted for the first time,and the test results of the predictability based on additional pretreatment experiments proved that the developed PLS model achieved a good predictive performance(particularly for the final total sugar yield),indicating that the developed PLS model can be used to predict the effectiveness of HSC pretreatment.Therefore,multivariate analysis can be potentially used to monitor and control the pretreatment process in future large-scale biorefinery applications.

Biotreatment of Wastewater from Soda-pretreatment Process of Corn Stover Using White-rot Fungus Z-6

Alkaline pretreatment of straw materials prior to enzyme hydrolysis is a key step for bioconversion of lignocellulose to bioethanol and chemicals.Wastewater from the alkaline pretreatment process must be treated before discharge to minimize its environmental impact.In this study,biotreatment of the wastewater from soda-pretreatment process of corn stover was investigated using fungus Z-6,and some indexes such as color,chemical oxygen demand(COD),and lignin content of wastewater before and after biotreatment were determined to assess the effect of the biotreatment.Results showed that fungus treatment could remove color up to approximately 72%after 2 d,and decrease COD and lignin content by about 63%and 60%,respectively after 3 d.The wastewater was fractionated using dynamic ultrafiltration method,and the changes in lignin contents of the effluent fractions with different molecular weights before and after biotreatment were analyzed.Some compounds produced by the fungus during treatment were identified using gas chromatography-mass(GC-MS)spectrometer,which revealed that depolymerization of lignin occurred during the biotreatment process.

A Brief Introduction of Extrusion and Micro-storage Processing Technology of Corn Stover

A new corn stover roughage processing method, corn stover extrusion and micro-storage processing technology, was introduced from the aspects of basic working principle, production and processing process, characteristics of cornstalk via extrusion and micro-storage processing. The technology was proved to be a feasible and practical processing technology of stover feed with broad prospect.

Study of the Effect of Different Solids Load on the Optimum pH during Enzymatic Hydrolysis of Steam Exploded Corn Stover

The understanding of enzymatic saccharification of pretreated lignocellulosic material is of great importance. There are several important commercially available enzymes in the market that are used for this purpose. The conditions of pH and temperature performance of any particular enzyme are very well defined and it is clearly indicated by its manufacturer and it depends on the type of enzyme or enzymes in the complex pool. It is well know that commercial cellulases work best at pH around 4.8-5.0 and as a consequence this is widely used in the industry and the literature. In this study it was found that optimum pH of cellulases is different than that recommended by its manufacturer at higher solids load saccharification. The optimum pH changes depending on the consistency or solids loads of the matrix where the enzyme is acting upon. Steam exploded corn stover was tested with cellulases and xylanases at different pH, consistencies and ionic strength. Results showed that the optimum pH at lower consistency （1% w/w） is the same as the one recommended by the manufacturer and in the literature; however at higher consistency the value obtained was higher （pH 5.5 to pH 6.5） instead ofpH 4.8. The difference could represent up to 30-50% higher yields and hence of great importance for the economics of second generation fuel production. An explanation of this behavior could be associated with the Donnan effect theory. This effect indicates that the presence of charged groups in the fiber matrix creates a pH gradient within the slurry. If the charged groups are negatively charged this would create a local or internal pH lower than the surrounding liquid pH. This could explain why by reducing the concentration of H^＋ higher enzymatic conversion yields were observed.

The Effect of Urea Treatment on the Chemical Composition and Rumen Degradability of Sorghum Stover

The objectives of the study were to investigate the effects of different levels of urea treatments on chemical composition, nutritional value and rumen degradability of sorghum stover. Two groups of animals were used in this experiment. The first group, which served as control, was offered untreated sorghum stover. The other, the experiment group recived sorghum stover to which was added 2%, or 4% urea. Crude protein （CP） content of the treated sorghum was enhanced （P 〈 0.05） over the untreated one, and ranked as 7.30% and 6.05% CP for 4% and 2% respectively. Nutrient detergent fiber （NDF） content was decreased （P 〈 0.05） from 92.5% （control） to 89.8% and 87.8% for 2% and 4% urea respectively.Ether extract （EE） content was decreased （P 〈 0.05） from 1.77% （control） to 1.63% and 0.82% for 2% and 4% respectively. The rumen degradability was increased （P 〈 0.05） from 59.2% （control） to 64.2%, and 67.2% for 2%, and 4% sorghum and in hours 0, 4, 8, 16, 24, 48, 72 and 96.

Consolidated bioprocess of corn stover to polysaccharide using Chaetomium globosum CGMCC 6882

Polysaccharide produced from medicinal endophytic fungus not only has applications in foods,but also exhibits multiple biological activities.In this work,an endophytic fungus Chaetomium globosum CGMCC 6882 could use corn stover to produce a polysaccharide(GCP-SC)by consolidated bioprocess and the titer of GCP-SC reached 3.2 g/L.The transcriptional levels of genes related to cellulose degradation(cbh,cdh,glu and egl)in C.globosum CGMCC 6882 were 4.38,3.85,3.13,and 2.17 folds compared to the control group when corn stover was used as the sole carbon source.Moreover,GCP-SC showed a time-and dose-dependent manner of inhibitory effect on A549 cells and the inhibitory rate reached 93.3%.This work provides meaningful data on agricultural residues utilization and facilitation of future relative resource conversion studies.