Presence Of Wheat Straw Research Articles

Assessment of Microbial Diversity during Thermophilic Anaerobic Co-Digestion for an Effective Valorization of Food Waste and Wheat Straw

In this study, predominant bacterial and archaeal populations and their roles during anaerobic mono-digestion of food waste (FW) and co-digestion of FW with straw pellets (SP) at thermophilic temperature (53 ± 1 °C) were assessed by Next Generation Sequencing (NGS) analysis at organic loading rates (OLRs) of 3.0 and 7.0 gVS/L/d. Depending on the seed; results revealed that Firmicutes, Bacteroidetes, and Proteobacteria were, respectively the most prevalent bacterial phyla at both OLRs investigated. On the other hand, Euryarchaeota was dominated by methanogens playing crucial role in biogas production and correlated mainly with the activities of Methanobacteria and Methanomicrobia at class level. Acetoclastic Methanosaetae was the predominant genus at OLR = 3.0 gVS/L/d; however, shared the same predominance with hydrogenotrophic methanogens Methanospirillium at the highest OLR. Although no clear effect in response to straw addition at OLR of 3.0 gVS/L/d could be seen in terms of methanogenic archaea at genus level, hydrogenotrophic methanogens revealed some shift from Methanobacterium to Methanospirillium at higher OLR. Nevertheless, no prominent microbial shift in the presence of wheat straw at increased OLR was likely due to adapted inoculation at start-up which was also demonstrated by relatively stable biogas yields during co-digestion.

Effect of aging on stabilization of Cd and Ni by biochars and enzyme activities in a historically contaminated alkaline agricultural soil simulated with wet-dry and freeze-thaw cycling.

Natural aging alters the surface physicochemical properties of biochars, which can affect the retention of heavy metals. This work investigated the effect of biochar aging on stabilization of heavy metals (Cd and Ni) and soil enzyme activities simulated with laboratory wet-dry (WD) and freeze-thaw (FT) cycling. A wheat straw (WS) biochar and a corn straw (CS) biochar were subjected to 30 WD or FT cycles, and Cd- and Ni-contaminated alkaline soils amended with the two fresh biochars (at 5% w/w) were subjected to 30-day constant moisture incubation and 30 WD or FT cycles. WD and FT aging caused slight reduction in the pH of the biochars, significant increases in their O contents and surface areas, and formation of new carbonate minerals. WS biochar was more effective than CS biochar at reducing the phytoavailable Cd in the soil, with reduction of 12.1%, 14.6%, and 12.9% under constant moisture incubation, WD aging, and FT aging, respectively. Reduction in phytoavailability of Ni by the addition of biochars was observed only under WD aging, by 17.0% and 18.5% in the presence of WS and CS biochars, respectively. Biochar amendment also reduced the distribution of Cd in the acid soluble and reducible fractions in all aging regimes. The addition of biochars decreased catalase activity in almost all aging regimes and invertase activity under FT aging, but increased urease activity under FT aging. Comparison of the enzyme activities in the soils amended with biochars under constant moisture and accelerated aging conditions indicates WD aging significantly decreased the activities of catalase, invertase, and urease in all treatments, while FT aging significantly increased urease activity in all treatments. These findings suggest that biochars can stabilize Cd in alkaline soils under changing environmental conditions, although the activities of some soil enzymes could be negatively impacted.

Presence of wheat straw in soil influences nutrient availability and leaching in soil mulched with high or low C/N organic materials

ABSTRACT The study aimed to determine nutrient availability in soil mulched with organic materials and how this is influenced by the presence of high C/N residue in the soil. Three organic materials were used: mature wheat straw (W, C/N 81), young faba bean shoots (FB, C/N 7) and sheep manure (SM, C/N 8). There were eight treatments: unamended control, soil containing W, soil containing W and mulched with W, FB or SM and soil only with W, FB or SM mulch. Soils were leached on days 4, 12, 20 and 28 and sampled 8 days after each leaching. Cumulative respiration over 36 days was influenced by mulch type: FB > W > SM and higher in soil mixed with W and mulched than in soil with only mulch. Microbial biomass N was two-fold higher in soil mixed with wheat and mulched than in soil with only mulch. Available N was between 0.2 and two-fold higher in soil with only mulch than soil with mulch and mixed with W. Available N increased over time with FB mulch but changed little with SM or W mulch. In conclusion, W in the soil can enhance N immobilisation and thus reduce N leaching from FB mulch.

Effects of some industrial and organic wastes application on growth and heavy metal uptake by tomato (Lycopersicum esculentum) grown in a greenhouse condition.

In this study, pot experiments were conducted to determine the effects of industrial solid wastes (ISWs) (ceramic, stone, and sugar factory wastes) and organic wastes (rice husk and wheat straw) on growth and heavy metals uptake by tomato (Lycopersicum esculentum) plants. The soil was treated with 10% of ISWs and 5% of organic wastes. The fractionation of heavy metals also has been studied in all treated soils. It was observed that the addition of ISWs in soil increased heavy metal contents in all fractions. The addition of organic wastes to control and treated soils decreased exchangeable fraction and increased organic matter and residual fractions. Following the ceramic factory and stone cutting waste addition, tomato yield significantly decreased as compared to control soil. The application of ISWs caused an increase in heavy metal contents of tomato plants. In control and ISWs-treated soils, dry matter yield of tomato grown in the presence of wheat straw was significantly restricted, while the application of rice husk increased tomato shoot and root dry weight. Results of experiments indicated that the application of both organic wastes significantly decreased heavy metal uptake by tomato plants. The investigation of health risk index (HRI) values indicated that in these industrial areas, potential health risk by intake of heavy metals from tomato for both adults and children generally assumed to be safe. The values of HRI were lesser when rice husk was applied to the soil. In general, these results highlighted that the application of rice husk in soils contaminated with ISWs increased the growth and yield of tomato and reduced the heavy metal toxicity for tomato consumption in contaminated soils.

Influence of mulch C/N ratio and decomposition stage on plant N uptake and N availability in soil with or without wheat straw

AbstractMulches can improve soil properties, but little is known about nutrient availability in mulched soil that contains plant residues and the effect of mulching with manures. The aim of this study was to determine the effects of mulching with high or low C/N organic materials, in which low C/N materials differed in decomposability, and the presence of wheat straw in the soil on plant growth and N uptake, soil N availability and microbial biomass N within about four months after mulching. Three organic materials were used: mature wheat straw (W, C/N 80), young faba bean shoots (FB, C/N 7), and sheep manure (SM, C/N 8). There were eight treatments differing in amendment methods (mulching or mixing with W or both) and mulching materials (W, FB or SM). Treatments that were only mulched with W, FB or SM are referred to as m‐treatments. In m/s‐treatments, after W was mixed into the soil, W, FB or SM were placed on the soil surface as mulch. Two other treatments included an unamended control and soil mixed with W. Wheat was planted 0, 35 or 70 days after mulching (referred to as 0, 35, and 70 DAM) and grown for 35 days. Faba bean mulch increased shoot dry weight, shoot N uptake and available N compared to wheat or sheep manure mulch, particularly in the m‐treatments. Shoot dry weight was higher in m‐treatments than corresponding m/s‐treatments with the same mulch type. Shoot N uptake was higher in 70 DAM than in 0 DAM in all treatments and 0.3 to three‐fold higher in m‐treatments than the corresponding m/s‐treatments. Microbial biomass N was higher in 0 DAM than in 35 and 70 DAM in most treatments and up to two‐fold higher in m/s‐treatments than the corresponding m‐treatments. Available N in m/s‐treatments was two to six‐fold higher than m‐treatments in 0 DAM, but differed little in older mulch ages of W and SM. It can be concluded that compared to soil with only mulch, mixing of wheat straw into soil reduced plant growth and N uptake, particularly in the early stages of mulching (0 and 35 DAM). However, the presence of wheat in mulched soil may provide a longer lasting source of N for plants and reduce the risk of N leaching from rapidly decomposing low C/N mulch due to greater microbial biomass N uptake than only soil with mulch.

Hydrogen production via supercritical water gasification of almond shell over algal and agricultural hydrochars as catalysts

Almond shell is one of the most abundant agricultural wastes in Kurdistan province of Iran. Conversion of almond shell into hydrogen-rich gas via supercritical water gasification (SCWG) was investigated in this study using a tubular batch micro-reactor system. Non-catalytic tests were carried out in different conditions to determine the optimum condition for H2 production. Maximum hydrogen yield of 7.85 mmol/g, was observed in the temperature of 460 °C, residence time (RT) of 10 min and feed/water ratio (F/W) of 0.01. Catalytic experiments were performed using hydrochars as solid residues remained after SCWG of Cladophora glomerata (C. glomerata) macroalgae and wheat straw. Hydrochars were characterized by ICP-OES, FESEM and BET methods. For catalytic experiments, hydrochars were added to the almond shell by the weight ratio of 0.4. Conversion of almond shell and hydrogen production, were more influenced by the presence of inorganic compounds in the hydrochars rather than the surface area and pore volume. The maximum hydrogen yields of 10.77 and 11.63 mmol/g, were observed for catalytic experiments in the presence of wheat straw and C. glomerata hydrochars, respectively.

Wheat straw degradation and production of alternative substrates for nitrogenase of Rhodobacter sphaeroides.

Cellulose is a major component of plant biomass and could be applied in the production of biofuels, especially bioethanol. An alternative approach is production of a clean fuel - hydrogen from cellulosic biomass. In this paper an innovatory model of cellulosic waste degradation has been proposed to verify the possibility of utilization of cellulose derivatives by purple non-sulfur bacteria. The concept is based on a two-step process of wheat straw conversion by bacteria in order to obtain an organic acid mixture. In the next stage such products are consumed by Rhodobacter sphaeroides, the known producer of hydrogen. It has been documented that Cellulomonas uda expresses cellulolytic activity in the presence of wheat straw as an only source of carbon. R. sphaeroides applied in this research can effectively consume organic acids released from straw by C. uda and Lactobacillus rhamnosus and is able to grow in the presence of these substrates. Additionally, an increased nitrogenase activity of R. sphaeroides has been indicated when bacteria were cultivated in the presence of cellulose derivatives which suggests that hydrogen production occurs.

Influence of an organic amendment comprising saprophytic and mycorrhizal fungi on soil quality and growth of Eucalyptus globulus in the presence of sewage sludge contaminated with aluminium

The single application of either sewage sludge with high aluminium concentration, wheat straw or the mixture of both residues to soil did not increase the growth of Eucalyptus globulus Labill. However, inoculation with either the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis, the saprobe fungi Coriolopsis rigida (Berk. Et Mont.) Murrill and Phanerochaete chrysosporium Burds or the combination of each saprobe with the AM fungus increased both the P concentration and dry weight of E. globulus shoots. These effects were greater in the presence of wheat straw or sewage sludge, but were greatest in the presence of the mixed residue. Phanerochaete chrysosporium had the greatest effect on plant dry weight when co-inoculated with R. irregularis in the treatment with mixed residue. The co-inoculation of AM and saprobe fungi increased fluorescein diacetate and β-glucosidase activities in the bulk soil of E. globulus grown in the treatment with mixed residue. However, only the AM fungus increased dehydrogenase activity, and phosphatase activity was similar in all treatments tested. Our results showed that sewage sludge with high aluminium concentration could be used as a soil amendment to improve the growth of E. globulus when mixed with wheat straw and co-inoculated with saprobe and arbuscular fungi.

Enhanced Heterotrophic Denitrification for the Treatment of Nitrate Contaminated Groundwater by Wheat Straw

The method of the heterotrophic denitrification remediation of nitrate-polluted groundwater involves the study of organic carbon sources as electron donor. The aim of the present study was to evaluate wheat straw for its ability to enhance denitrification in column experiments. The inlet concentration was 50.0 mgNO3--N/L and the column operated at the flow rate of 2.0 ml/min. The result showed that in the presence of wheat straw, highly reducing conditions were generated and complete removal of nitrate (>95%) was achieved, with less accumulation of nitrite. Consequently, wheat straw is an attractive carbon source for groundwater denitrification.

Production of Enzymes from Rice Husks and Wheat Straw in Solid State Fermentation

In Europe, the agricultural wastes represent a significant potential for the development of biorefineries in different sectors such as cereals. Recovery of phytochemicals as well as the energetic valorization of the plant matrixes needs the demolition of the wall cell plants. Hydrolitic demolition by lignocellulosic enzymes is one of the most studied approach. White rot fungi such as Pleurotus ostreatus produce a wide range of extracellular enzymes to degrade complex lignocellulosic substrates into soluble substances that can be used as nutrients.The objective of this study is to induce the production of lignocellulosic enzymes through the growth Pleurotus ostreatus in solid state fermentation using agro-food wastes as substrates: rice husks and wheat straw. The activities of cellulase, xylanase, peroxidase, laccase, and arylesterase are determinate by specific colorimetric assays.All trials showed a scarce productivity of cellulase while all the detected enzymatic activities resulted higher using rice husk as a substrate than in presence of wheat straw. Pleurotus ostreatus exhibited a prevalent production of arylesterase activity and, in particular, the contemporary presence of significant xylanase and feruloilesterase activities was probably due to the typical ferulic bond and diferulic bridge in the heteroxylane structure of monocot’s plant cell walls such as rice and wheat. Moreover, in terms of yields arylesterase activities for both substrates, are prevalent on other activities.Our findings showed that the enzymatic production was strictly dependent to the periodic removal of the produced enzymes. The development of new solid state bioreactor design for a steady state production of enzymes from Pleurotus ostreatus could open an interesting industrial approach.

English

A microbial community named WSD-5 was successfully selected from plant litter and soil after longterm directed acclimation at normal temperature. After 15 days of cultivation at 30°C, the degradation rate of wheat straw by WSD-5 was 75.6%. For cellulose, hemicellulose and lignin, the degradation rates were 94.2, 81.9 and 21.3%, respectively. The optimal pH for filter paper, CMCase, avicelase, β- glucosidase and xylanse activities was 6.24, 6.24, 5.91, 5.91 and 6.24, respectively. The optimal reaction temperature for all enzyme activity was 55°C. Filter paper enzyme, cellulase and xylanase were secreted from the degradation of wheat straw by WSD-5. The highest filter paper, cellulose endonuclease (CMCase), cellulose exonuclease (avicelase), β-glucosidase and xylanase activities were 1.30, 4.35, 0.60, 0.43 and 15.16 U/ml, respectively. A library of bacterial and fungal ribosomal gene sequences obtained from the community showed the presence of Ochrobactrum sp, Coprinus cinereus and Pseudallescheria boydii . To our knowledge, this was the first report of a microbial community which consisted of bacteria and fungi and was selected in the presence of wheat straw to produce extracellular filter paper enzyme, cellulase and xylanase. Key words: Microbial community, lignocellulose degradation, filter paper activity, CMCase, avicelase, β- glucosidase, xylanase.

Performance characterizations of particleboards made with wheat straw and waste veneer splinters

The aim of this study was to determine the performance of three-layer particleboard made from wheat straw and veneer splinters, as waste materials. For the purpose of evaluation, compositions of wheat straw and beech veneer splinters at different mixture rates were compared for some of properties. Physical (thickness swelling and water absorption) and mechanical properties (modulus of rupture, modulus of elasticity, internal bond and impact strength) of the boards were evaluated. Effects of mixing ratios of fibrous material and press temperature on the above-mentioned properties were also investigated. The mixing ratios of beech veneer with wheat straw were 100%:0%, 75%:25%, 50%:50%, 25%:75% and 0%:100%, respectively. A commercial urea–formaldehyde (UF) adhesive was used as binder. A total of 10 experimental boards with an average target density of 0.70gcm−3 across all mixtures were fabricated. All the mechanical and physical properties of the boards were improved when the press temperature was increased from 140 to 170°C. Analysis of data revealed that the mechanical properties were significantly different among the board types. With the exception of modulus of elasticity, the other properties were decreased by the addition of wheat straw particles. In general, water absorption and thickness swelling decreased with the increase of wheat straw content. The presence of wheat straw in the particleboards resulted in higher water absorption and thickness swelling. Finally, it can be stated that wheat straw and beech veneer splinters have potential as supplement fibrous materials, in combination with wood particles for particleboard manufacturing and indoor applications.

Enriched Microbial Community in Bioaugmentation of Petroleum-Contaminated Soil in the Presence of Wheat Straw

The bioaugmentation of petroleum-contaminated soil using Enterobacter cloacae was profiled from the evolution of microbial community, soil dehydrogenase activity, to the degradation of petroleum contaminants. The seeding and proliferation of inoculant and the consequential microbial community were monitored by denaturing gradient gel electrophoresis analysis of the amplification of V3 zone of 16S rDNA. Degradation process kinetics was characterized by the degradation ratio of nC17 to nC18. The dehydrogenase activity was also determined during the degradation process. An abrupt change in the microbial community after inoculation was illustrated as well as successive changes in response to degradation of the petroleum contaminants. Seeding with E. cloacae stimulated the growth of other degrading stains such as Pseudomonas sp. and Rhodothermus sp. The application of wheat straw as a representative lignin waste, at 5% (w/w), induced an increase in the total dehydrogenase activity from 0.50 to 0.79, an increase in the microbial content of 130% for bacteria and 84% for fungi, and an increase of the overall degradation ratio from 44% to 56% after 56 days of treatment. The above mentioned results have provided a microbial ecological insight being essential for the design and implementation of bioaugmentation processes.

Response of transgenic potato seedlings to allelopathic pressure and the effect of nutrients in the culture medium

Chinese farmers frequently use a wheat–potato cropping system. The land area planted to transgenic potatoes is increasing because transgenic potatoes have greater resistance to pests and diseases. However, little is known about the bio-compatibility of transgenic potatoes with wheat straw. The objective of this tissue culture study was to determine the allelopathic effects of wheat straw on transgenic potato seedlings. Seedlings were cultured on normal MS medium (normal treatment) and nutrient-deficient MS medium (acclimated treatment) and then transferred to MS medium, which contained wheat straw powder. Wheat straw powder inhibited potato seedling growth in both treatments. Among the parameters analyzed in this study, inhibition was greatest for plant fresh weight and least for plant height. The inhibitive effects of wheat straw were greater for seedling roots compared to shoots. Resistance to allelopathic pressure from wheat straw was greater in acclimated seedlings compared to normal seedlings. This suggested that previous pressure may have induced tolerance in the transgenic potato seedlings. Furthermore, growth inhibition of potato seedlings from the normal treatment increased as the amount of wheat straw powder in the culture medium increased. Calculations indicated that the presence of wheat straw would lead to a 55% reduction in the total biomass of normal potato seedlings compared to a 39% reduction for acclimated seedlings. Parameters such as net photosynthesis rate (Pn) and quantum yield (Y(II)) changed as the nutrient content of the culture medium increased or decreased, but the changes in the parameters were smaller for acclimated seedlings compared to normal seedlings. This suggests that nutrient status during the culture period could help transgenic potato seedlings adapt and compensate for energy loss from seedlings in defending against allelopathic pressure. In summary, the results show that previous exposure to pressures such as nutrient deficiency may increase the allelopathic pressure resistance of transgenic potato seedlings.

Modulation of cellulosome composition in Clostridium cellulolyticum: Adaptation to the polysaccharide environment revealed by proteomic and carbohydrate‐active enzyme analyses

Clostridium cellulolyticum is a model mesophilic anaerobic bacterium that efficiently degrades plant cell walls. The recent genome release offers the opportunity to analyse its complete degradation system. A total of 148 putative carbohydrate-active enzymes were identified, and their modular structures and activities were predicted. Among them, 62 dockerin-containing proteins bear catalytic modules from numerous carbohydrate-active enzymes' families and whose diversity reflects the chemical and structural complexity of the plant carbohydrate. The composition of the cellulosomes produced by C. cellulolyticum upon growth on different substrates (cellulose, xylan, and wheat straw) was investigated by LC MS/MS. The majority of the proteins encoded by the cip-cel operon, essential for cellulose degradation, were detected in all cellulosome preparations. In the presence of wheat straw, the natural and most complex of the substrates studied, additional proteins predicted to be involved in hemicellulose degradation were produced. A 32-kb gene cluster encodes the majority of these proteins, all harbouring carbohydrate-binding module 6 or carbohydrate-binding module 22 xylan-binding modules along dockerins. This newly identified xyl-doc gene cluster, specialised in hemicellulose degradation, comes in addition of the cip-cel operon for plant cell wall degradation. Hydrolysis efficiencies determined on the different substrates corroborates the finding that cellulosome composition is adapted to the growth substrate.

Urease and nitrification inhibitors to reduce emissions of CH4 and N2O in rice production

Strategies used to reduce emissions of N2O and CH4 in rice production normally include irrigation management and fertilization. To date, little information has been published on the measures that can simultaneously reduce both emissions. Effects of application of a urease inhibitor, hydroquinone (HQ), and a nitrification inhibitor, dicyandiamide (DCD) together with urea (U) on N2O and CH4 emission from rice growing were studied in pot experiments. These fertilization treatments were carried out in the presence and absence of wheat straw, applied to the soil surface. Without wheat straw addition, in all treatments with inhibitor(s) the emission of N2O and CH4 was significantly reduced, as compared with the treatment whereby only urea was applied (control). Especially for the U+HQ+DCD treatment, the total emission of N2O and CH4 was about 1/3 and 1/2 of that in the control, respectively. In the presence of wheat straw, the total N2O emission from the U+ HQ+ DCD treatment was about 1/2 of that from the control. The total CH4 emission was less influenced. Wheat straw addition, however, induced a substantial increase in emissions of N2O and CH4. Hence, simultaneous application of organic materials with a high C/N ratio and N-fertilizer (e.g. urea) is not a suitable method to reduce the N2O and CH4 emission. Application of HQ+DCD together with urea seemed to improve the rice growth and to reduce both emissions. The NO3-- N content of the rice plants and denitrification of (NO3- +NO2-)-N might contribute to the N2O emission from flooded rice fields.

Algal growth control by a barley straw extract

In recent years, there has been an apparent increase in the occurrence of harmful algal blooms occurring in potable waters. The potential of a simple barley straw extract to inhibit algal growth was assessed. Algal growth in lakewater was inhibited by the addition of barley straw (1% w/v), with the chlorophyll a concentration remaining below the original level ( 40 μg l −1 ) throughout the experiment. In contrast, in the presence of wheat straw, algal biomass increased, reaching a final chlorophyll a concentration of 1160 μg l −1 after 28 days. Analysis of the remaining particulate straw at the end of the experiment showed that the lignin content of barley straw had increased significantly from 10–33% (w/w). Further, a preparation of a simple aqueous extract from the decomposed-barley straw was found to inhibit the cyanobacteria Microcystis sp. and the algal species Scenedesmus, with chlorophyll a levels some 10-fold lower than in untreated flasks. This study shows that a decomposed-barley extract, even in a very dilute concentration (0.005%) was capable of inhibiting the growth of Microcystis sp., a commonly occurring cyanobacterium which produces the toxin microcystin and has been responsible for some of the most serious pernicious algal blooms in the UK.

Denitrification and nitrogen immobilization as affected by organic matter and different forms of nitrogen added to an anaerobic water-sediment system

The effects of wheat straw and different forms of N on denitrification and N immobilization were studied in an anaerobic water-sediment system. The water-sediment system was supplemented with various combinations of wheat straw and 15N-labelled and unlabelled (NH4)2SO4 or KNO3, and incubated anaerobically at 30°C for 10 days. 15N-labelled and unlabelled NO inf3 sup- , NO inf2 sup- , NH inf4 sup+ , and organic N were determined in the water-sediment system. The gases evolved (N2, CO2, N2O, and CH4) were analyzed by gas chromatography at regular intervals. Larger quantities of 15N2−N and organic 15N were formed in wheat straw-amended systems than in non-amended systems. Trends in CO2 production were similar to those of N2−N evolution. The evolution of N2O and CH4 was negligible. Denitrification processes accounted for about 22 and 71% of the added 15NO inf3 sup- −N in the absence and presence of wheat straw, respectively. The corresponding denitrification rates were 3.4 and 12.4 μg 15Ng-1 dry sediment day-1. In systems amended with 15NO inf3 sup- −N and 15NO inf3 sup- +NH inf4 sup+ −N without wheat straw, 1.82 and 1.58%, respectively, of the added 15NH inf3 sup- −N was immobilized. The corresponding figures for the same systems supplemented with wheat straw were 5.08 and 4.10%, respectively. Immobilization of 15NO inf4 sup+ −N was higher than that of 15NO inf3 sup- −N. The presence of NO inf3 sup- −N did not stimulate NH inf4 sup+ −N immobilization.

β‐Glucosidase production by Trichoderma reesei QM9414 on wheat straw. Location and some kinetic features

AbstractIn this paper we studied the conditions for the production of β‐glucosidase from T. reesei QM9414 in batch cultures using milled and sieved wheat straw as sole carbon source. High β‐glucosidase production in the presence of wheat straw, a more realistic substrate than commercial cellulose, was obtained.The influence of particle size of wheat straw on β‐glucosidase production in cell‐free, cell and cell‐wall extracts was studied. The particle size of wheat straw notably influenced enzyme production in cell and extramycelial extracts but it was less important with respect to the cell wall bound enzyme.β‐glucosidase production was studied along of the fermentation. The results suggest a close relation between β‐glucosidase from cell extract and extramycelial broth; geneticin levels of inhibition of β‐glucosidase biosynthesis in both fractions were similar, a fact that suggests a common origin for the enzyme.Kinetic parameters for β‐glucosidase from cell free and cell extracts were Vmax = 0.28 μmol/min/mg, KM = 0.91 mM and Vmax = 0.095 μmol/min/mg, KM = 0.39 mM respectively. Kinetic parameters for β‐glucosidase from cell‐wall could not be calculated because experimental data did not fit the different monosubstrate equations.

Soil Reception and Activity of Acetochlor, Alachlor, and Metolachlor as Affected by Wheat (Triticum aestivum) Straw and Irrigation

Acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide], alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] were applied in 280 L of water/ha to plots covered with 0 to 6720 kg/ha of wheat (Triticum aestivumL.) straw. At straw levels of 1120 kg/ha or greater, 50% or less of the applied herbicides were received by the soil surface before irrigation. Sprinkle irrigation (1.3 cm) washed 15 to 20% of the originally applied herbicide into the soil regardless of straw level. More metolachlor was retained on the straw than acetochlor or alachlor. Analysis of the wheat straw indicated that little water-extractable herbicide remained for all herbicides. Initial herbicidal activity on grain sorghum [Sorghum bicolor(L.) Moench.] was reduced by the presence of wheat straw at the time of application, with acetochlor being least affected and alachlor most affected. Ten days after treatment, less than 10% of the original alachlor and acetochlor remained in the soil. When planted at this time, grain sorghum response was inversely related to the amount of straw mulch that was originally present. Metolachlor residues in the soil on day 10 were 11 to 26% of that on day 0 and there was comparably less reduction in activity on grain sorghum.