Digestion Of Residues Research Articles

Review on greenhouse gas emissions from pig houses: Production of carbon dioxide, methane and nitrous oxide by animals and manure

Abstract The environmental impacts of livestock production are attracting increasing attention, especially the emission of greenhouse gases (GHGs). Currently, pork is the most widely consumed meat product in the world, and its production is expected to grow in the next few decades. This paper deals with the production of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) by animals and by manure from pig buildings, with a focus on the influence of rearing techniques and nutrition. GHG emissions in piggeries originate from animals through CO2 exhalation and CH4 enteric fermentation, and from manure through the release of CO2, CH4 and N2O. The level of the CO2 exhalation (E-CO2, pig) depends on the physiological stage, the body weight (BW), the production level and the feed intake of the animals concerned. Enteric CH4 (E-CH4, pig) is principally related to dietary fibre intake and the fermentative capacity of the pig’s hindgut. Based on a review of the literature, the following equations are proposed in order to estimate E-CO2, pig (in kg day−1) and E-CH4,pig (in g day−1) for fattening pigs: E-CO2, pig = 0.136 × BW0.573; E-CH4,pig = 0.012 × dRes; with BW (in kg) and dRes for digestible residues (in g day−1). Numerous pathways are responsible for GHG production in manure. In addition, the microbial, physical and chemical properties of manure interact and modulate the level of emissions. Influencing factors for removal systems for both liquid and solid fractions of manure have been investigated. A large range of parameters showing an impact on the level of GHG production from pig houses has been reported. However, few of these can be considered unquestionably as GHG mitigation techniques because some strategies have shown contradictory effects depending on the gas, the circumstances and the study. Nevertheless, frequent manure removal seems to be an efficient means to reduce concurrently CO2-, CH4- and N2O-emissions from pig buildings for both slatted and bedded floor systems. Manure removal operations may be associated with specific storage conditions and efficient treatment in order to further reduce emissions. Several feeding strategies have been tested to decrease GHG emissions but they seem to be ineffective in reducing emissions both significantly and durably. In general, good management practices that enhance zootechnical performance will have beneficial consequences on GHG emission intensity. Taking into account the results described in the literature regarding CO2-, CH4- and N2O-production from animals and manure in pig houses, we estimate total GHG emissions to 448.3 kg CO2equiv. per slaughter pig produced or 4.87 kg CO2equiv. per kg carcass. The fattening period accounts for more than 70% of total emissions, while the gestation, lactation and weaning periods each contribute to about 10% of total emissions. Emissions of CO2, CH4 and N2O contribute to 81, 17 and 2% of total emissions from pig buildings, representing 3.87, 0.83 and 0.11 kg CO2equiv. per kg carcass, respectively.

Mitigation of Greenhouse Gas Emissions by Water Management in a Forage Rice Paddy Field Supplemented with Dry-Thermophilic Anaerobic Digestion Residue

Dry-thermophilic anaerobic co-digestion (DTAD) can be used to treat forage rice straw and pig manure and generate biogas as an energy source. Solid residue produced from DTAD process can be used as a fertilizer in forage rice fields, while addition of the residue could increase methane (CH4) and nitrous oxide (N2O) emissions from the soil. We evaluated the effects of adding DTAD residue and water management on CH4 and N2O emissions from a forage rice field. Three treatments were evaluated: (a) 100 kg N · ha−1 chemical fertilizer and continuous flooding (CC); (b) residue addition (300 kg N · ha−1 DTAD residue) with continuous flooding (RC); and (c) residue addition with intermittent irrigation (RI). RC and RI showed higher CH4 fluxes than CC throughout the growing period. After a midsummer drainage, RI showed higher soil Eh values and lower CH4 fluxes (mean, 7.6 mg C · m−2 · h−1) than those in RC (mean, 18.6 mg C · m−2 · h−1). Abundance of mcrA gene copy number was not different between RC and RI, suggesting CH4 flux was reduced by suppression of methanogenic activity by intermittent irrigation. Cumulative CH4 emissions during the cultivation period were 105, 509, and 306 kg C · ha−1 in CC, RC, and RI, respectively. N2O fluxes were within detection limits in all treatments. Our results, to our knowledge, are the first to show greenhouse gas emission from forage rice fields supplemented with DTAD residue and of the effectiveness of water management in CH4 mitigation.

Alkali extraction of valuable metals from spent Mo–Ni/Al2O3 catalyst

Extraction of metal values from the spent Mo–Ni/Al2O3 catalyst containing complex oxides was investigated in this work. Aiming at studying selective extraction of metals, a sequential recycle process is conceived as follows: First, acidic oxide MoO3 is selectively extracted by alkali leaching. Then amphiprotic Al2O3 is dissolved by caustic soda autoclaving. Al(OH)3 is obtained by seeding precipitation and used to prepare the support of new catalysts. Besides, Ni(OH)2 remains in the digestion residue as “green mud” of the modified Bayer process. In the light of the idea, alkali leaching experiments were conducted, using several common basic leaching agents. The results show that caustic autoclaving at low NaOH/Mo ratio could selectively extract Mo without significant dissolution of the matrix. Under the optimum operating conditions of temperature 160°C, NaOH dosage 1.2 times the stoichiometric amount, solid/liquid ratio 1:4, retention time 120min and stirring rate 300rpm, over 96% of Mo was recovered while less than 0.2% of Al was dissolved. After leaching of Mo, the Al2O3 matrix was dissolved completely by caustic soda autoclaving at 160°C. Sodium aluminate solution was purified by CaO and Ba(OH)2. The overall Mo and Al extraction yields were up to 99%.

Industrial sludge containing pharmaceutical residues and explosives alters inherent toxic properties when co-digested with oat and post-treated in reed beds

BackgroundMethane production as biofuels is a fast and strong growing technique for renewable energy. Substrates like waste (e.g. food, sludge from waste water treatment plants (WWTP), industrial wastes) can be used as a suitable resource for methane gas production, but in some cases, with elevated toxicity in the digestion residue. Former investigations have shown that co-digesting of contaminated waste such as sludge together with other substrates can produce a less toxic residue. In addition, wetlands and reed beds demonstrated good results in dewatering and detoxifying of sludge. The aim of the present study was to investigate if the toxicity may alter in industrial sludge co-digested with oat and post-treatment in reed beds. In this study, digestion of sludge from Bjorkborn industrial area in Karlskoga (reactor D6) and co-digestion of the same sludge mixed with oat (reactor D5) and post-treatment in reed beds were investigated in parallel. Methane production as well as changes in cytotoxicity (Microtox(R); ISO 11348–3), genotoxicity (Umu-C assay; ISO/13829) and AhR-mediated toxicity (7-ethoxyresorufin-O-deethylase (EROD) assay using RTW cells) were measured.ResultsThe result showed good methane production of industrial sludge (D6) although the digested residue was more toxic than the ingoing material measured using microtox30min and Umu-C. Co-digestion of toxic industrial sludge and oat (D5) showed higher methane production and significantly less toxic sludge residue than reactor D6. Furthermore, dewatering and treatment in reed beds showed low and non-detectable toxicity in reed bed material and outgoing water as well as reduced nutrients.ConclusionsCo-digestion of sludge and oat followed by dewatering and treatment of sludge residue in reed beds can be a sustainable waste management and energy production. We recommend that future studies should involve co-digestion of decontaminated waste mixed with different non-toxic material to find a substrate mixture that produce the highest biogas yield and lowest toxicity within the sludge residue.

Recycling of Dry-Batch Digestate as Amendment: Soil C and N Dynamics and Ryegrass Nitrogen Utilization Efficiency

In this work a residue of dry-batch anaerobic digestion (DB) from the organic fraction of municipal solid waste, its composted homologous (CDB), and a municipal solid waste compost (MSWC) were characterized for their main physico-chemical traits and biological stability [oxygen uptake rate (OUR)]. These were then compared in soil incubations at 200 mg N kg−1, to assess carbon (C) and nitrogen (N) mineralization. The products’ nitrogen apparent recovery fraction (ARF) was assessed in a pot trial on Italian ryegrass. DB showed the highest OUR, followed by CDB and the more stable MSWC: 161.7; 20.7 and 5.7 mmol O2 kg−1 VS h−1, partially in agreement with the potentially mineralizable C pools in soil: 58.4; 16.6 and 19.5 % and their kinetics (k, 0.1906; 0.1405 and 0.1377 day−1). Composting greatly reduced the total carbon dioxide (CO2) emissions from 7,950 to 3,449 mg kg−1 in DB and CDB, even higher than MSWC (1,936 mg kg−1). After intense N-immobilization in soil (−22.3 %), DB finally reduced the gap (−6.9 %), also having a positive ARF (5.0 %), while CDB had greater N-immobilization (−12.9 %) and a negative ARF (−3.4 %). MSWC showed 3.8 % N-mineralization, and an intermediate ARF (2.7 %). The management of DB for plant nutrition therefore seems difficult since DB can furnish nitrogen not easily synchronizable with plant growth due to its release pattern characterized by initial immobilization. Composting increased stability but amplified N-immobilization due to the high C:N ratio of the bulking agent. A prolonged and more balanced composting process can reduce this restriction, aligning CDB with MSWC.

Evaluation of the effectiveness of a thermal hygienization reactor

For reasons of limiting the spread of serious transmissible diseases, with regard to the requirement for reducing landfill of biodegradable waste (which may or contains animal by-products and thus presents a potential risk to human and animal health) and with a focus on supporting its separate collection, there has been created a legal framework for processing and hygienization of materials containing animal by-products. For the above reasons new technologies are being developed and implemented. These technologies are able to ensure the processing of biological waste containing animal by-products. As a practical result of the effort to ensure the hygienization of biowaste, a hygienization unit of own design, which uses the thermal way of hygienization, is presented in this work. The general part of the work defines a legislative framework for the assignment and gives technical parameters and minimum requirements for conversion that hygienization unit should be able to perform, including the limits for digestion residues and compost.In the experimental section there are described operational tests which document the technological process of hygienization depending on the aeration of the contents of the reactor. Experiment III outlines the validation process which uses contamination by indicator organisms, including subsequent checking of their occurrence as well as processing of the results of experiments and evaluation of the process of hygienization.

Life cycle analysis of a biogas-centred integrated dairy farm-greenhouse system in British Columbia

This study investigates the potential integration of a dairy farm and a greenhouse into an eco-industrial system to promote waste-to-energy and waste-to-material exchanges. Natural gas consumption is substituted by renewable biogas generated from anaerobic digestion (AD) of the dairy manure; CO2 for plant enrichment in greenhouses is supplied by biogas combustion and the digestate (digestion residue) from digesters is used as animal bedding, plant growing media and liquid fertilizers.A life cycle analysis (LCA) was conducted to quantify the environmental impacts of the eco-industrial system in comparison to the conventional agriculture practices. The results show that the integrated system reduces non-renewable energy consumption, climate change impact, acidification, respiratory effects from organic emissions, and human toxicity by more than 40%. If the digestate surplus is treated as a waste, the integrated system shows an increase in eutrophication and respiratory effects from inorganic emissions while all the analyzed impacts are reduced if the digestate can be used for substituting chemical fertilizers.

Fluazuron-induced morphological changes in Rhipicephalus sanguineus Latreille, 1806 (Acari: Ixodidae) nymphs: An ultra-structural evaluation of the cuticle formation and digestive processes

Rhipicephalus sanguineus is a species of tick which is widely distributed in America, Africa and Australia and is probably the most prevalent among all the other ixodid tick species. The present study demonstrated the effects of the arthropod growth regulator fluazuron (Acatak®), in the formation of the integument and the digestive processes of R. sanguineus nymphs fed on rabbits treated with different doses of this chemical acaricide. For this, three different doses of fluazuron (20mg/kg, 40mg/kg and 80mg/kg) were applied “pour on” to the hosts divided into three different treated-groups (II, III, IV) of three animals each. A fourth group (I) of rabbits (n=3) was given distilled water as control. On the first day after treatment (24h), the hosts were artificially infested with R. sanguineus nymphs. After full engorgement (7 days), the nymphs were removed and placed on labeled Petri dishes and kept in BOD incubator for 7 days. The engorged nymphs were then taken to ultra-structural analysis. Results revealed the following main ultra-structural changes in the nymphs integument and midgut of the different treated groups (II, III, IV): cuticle disorganization and the absence of subdivisions, damages in the integument epithelial cells, size of digestive cells, amount of endosomes, autophagic and digestive vacuoles, accumulated digestive residues, lipid droplets and organelles found in the digestive cells’ cytoplasm, as well as the presence of microvilli in their plasma membranes. It is concluded that fluazuron may act on the integument and midgut cells of R. sanguineus engorged nymphs by impairing the synthesis of the new cuticle and the digestive processes (absorption of the blood ingested from the host, digestion – hemolysis, formation of digestive residues and release of nutrients to be converted into lipid, as well as for the synthesis of structural protein), which interfere in the development of nymphs, being able to prevent the emergence of adults after periodical ecdysis. These data indicate the possibility to use this arthropod growth regulator (AGR) in the control of R. sanguineus, at least in the nymphal stage of its biological cycle.

In vitro bacterial fermentation of tropical fruit fibres

Tropical fruits such as mango, papaya, pineapple and banana are rich sources of dietary fibre. However, few studies have examined the potential physiological effects of fibre from these tropical fruits. The aim of this study was to characterise the fermentability of dietary fibre found in banana, papaya, pineapple and mango as an estimate of the physiological effects of consuming these fruits. Freeze-dried fruit was subjected to in vitro digestion to remove digestible carbohydrates. Digestion residues were freeze-dried prior to fermentation. In vitro fermentation was carried for 24 h under anaerobic conditions to simulate conditions in the large intestine. Gas volume, pH and short chain fatty acids (SCFAs) concentration were measured at 0, 4, 8, 12, and 24 h. SCFAs were analysed by gas chromatography. There was no gas production from 0 to 8 h time points for all samples. Mango fibre resulted in more gas at 12 and 24 h than pineapple, papaya and banana fibres. The slurry pH was significantly lower for mango fibre at 12 and 24 h compared to other samples. Mango fibre resulted in significantly more propionate at 8 h compared to papaya and pineapple fibres. Butyrate concentrations were only significantly different at 4 h. At 24 h total and individual SCFA production did not differ among samples. All fruit fibres were fermentable, with mango fibre being the most rapidly fermented. Additional work is necessary to confirm a benefit on digestive health.

Improving Biogas Production and Biodegradability of Acid Hydrolytic Cotton Stalk with Addition of Nutritive Salts and Complex Anaerobic Cellulose Decomposing Bacteria

Nutritive salts and complex anaerobic cellulose decomposing bacteria (CACDB) were added for anaerobic digestion process in order to improve biogas production and biodegradability of acid hydrolytic cotton stalk. The results showed that addition of CACDB, nutritive salt I and nutritive salt II could effectively enhance daily biogas production, cumulative biogas and methane yields, in this treatment, the total gas production, daily average gas production, TS gas production rate, VS gas production rate and average yield of methane were all highest and reached 5908.90 mL, 196.96 ± 7.97 mL·d-1, 143.07 ± 5.79 mL·g-1, 156.32 ± 6.33 mL·g-1, 102.58 ± 3.34 mL·d-1, separately. The addition of CACDB and nutritive salts could improve the biodegradability of acid hydrolytic cotton stalk, in all addition treatments, the degradation rates of cellulose and lignin, VS reduction rates were higher and C/N ratios were lower than control treatment. The SEM analysis showed that the microstructure changes of digestion residues were helpful for biogas production.

Nitrogen and phosphorus recovery from anaerobic co-digestion residues of poultry manure and maize silage via struvite precipitation

Anaerobic digestion is commonly used for the stabilization of agricultural and animal wastes. However, owing to the stringent environmental criteria, anaerobic digester effluents need to be further treated to reduce nutrient loads to the receiving water bodies. Struvite precipitation is one of the promising techniques applied for this purpose. Yet, in the majority of cases, struvite precipitation is only applied to the liquid phase of anaerobic digester effluents. This study investigated the recovery of nutrients from both the liquid and the solid phases of the phase-separated effluent of a full-scale biogas plant co-digesting poultry manure and maize silage. Struvite precipitation in the liquid phase led to 72.1% and 95.1% average removal efficiencies of ammonium-nitrogen (NH4-N) and orthophosphate respectively. Changing the external phosphorus source did not make any statistically significant difference in nutrient removal. An acidic phosphorus-dissolution process was applied to the solid phase sample to obtain a phosphorus-enriched solution. More than 90.0% of both NH4-N and PO4-P were recovered from the phosphorus-enriched solution with the amendments of magnesium and phosphorus. In the experiments performed without any addition of external magnesium- and phosphorus-containing chemicals, almost complete (99.6%) PO4-P recovery and partial (14.6%) NH4-N recovery were obtained. The results of this study could contribute to the understanding of nutrient recovery from anaerobic digestion residues of manure and agricultural wastes by struvite precipitation.

Biochars prepared from anaerobic digestion residue, palm bark, and eucalyptus for adsorption of cationic methylene blue dye: Characterization, equilibrium, and kinetic studies

Biochars prepared from anaerobic digestion residue (BC-R), palm bark (BC-PB) and eucalyptus (BC-E) were used as sorbents for removal of cationic methylene blue dye (MB). The FE-SEM images indicated that the biochars have a well-developed pore structure, and the Brunauer-Emmett-Teller surface areas of BC-R, BC-PB, and BC-E were 7.60, 2.46, and 10.35 m(2)g(-1), respectively. The efficiencies of MB removal in the samples with initial concentrations of 5 mg L(-1) at pH 7.0 and 40°C by BC-R, BC-PB, and BC-E after 2h were 99.5%, 99.3%, and 86.1%, respectively. Pseudo-second-order kinetics was the most suitable model for describing the adsorption of MB onto the biochars. The experimental data were best described by the Langmuir isotherm model, with a maximum monolayer adsorption capacity of 9.50 mg g(-1) at 40°C for BC-R. The biochars produced from the three types of solid waste showed considerable potential for adsorption.

Assessment of the state of the art of technologies for the processing of digestate residue from anaerobic digesters

Anaerobic digestion is widely used as an important source of renewable energy. With the increasing number and capacity of biogas plants also, adequate treatment technologies for whole digestate - the residue from anaerobic digestion - are gaining attention. In this study the state of the art of digestate processing is analysed, and currently used treatment schemes and the various technological processes involved are evaluated. The study combines data and experiences from existing large-scale digestate processing facilities in Austria, Germany, Switzerland and Italy, as well as know-how from technology providers and relevant research projects. However, the field of digestate processing is still quite new and little detailed information about the performance of different technologies at industrial scale is available. Digestate processing is gaining importance since digestate utilisation can become an important bottleneck when increasing biogas production. In addition, the production of renewable fertiliser from digestate is increasingly of interest to replace fossil fertilisers. This study is the first profound attempt to establish an assessment of the state-of-the-art technologies in use.

Effect of anaerobic digestion residue vs. livestock manure and inorganic fertilizer on the hygienic quality of silage and haylage in bales

AbstractAn increased recycling of nutrients from organic waste to support feed and food production is important for achieving sustainability. However, organic waste may contain undesired microorganisms that may increase the risk of impaired hygienic quality of feeds when used in forage‐cropping systems. This study aimed to investigate how the hygienic quality of silage and haylage was affected after fertilization of grassland with organic fertilizers [anaerobic digestion residue (ADR) pasteurized before spreading, or liquid cattle manure] compared with inorganic NPK fertilization. The experiment was performed on the same grass ley for 2 years, with fertilization carried out before each harvest (year 1, two harvests; year 2, one harvest). The crop was conserved as silage (300 g DM kg−1) and haylage (500 g DM kg−1) in bales (ca 40–55 kg) stored for 1, 5 or 10 months before opening, including effects of storage time and conservation method (silage or haylage) on hygienic quality. Results showed that ADR‐treated crops did not produce silage or haylage with higher microbial counts in comparison with manure‐treated crops on any occasion. The fermentation pattern in silage and haylage from ADR‐treated crops was similar to the pattern in manure‐treated crops. The use of inorganic fertilizer sometimes produced lower pH and higher content of lactic acid in silage, compared with using organic fertilizers. In conclusion, ADR could be used as an organic fertilizer for forage crops without increased risk of impaired hygienic quality compared with using liquid manure or inorganic NPK fertilizers.

Anaerobically digested food waste in compost for Agaricus bisporus and Agaricus subrufescens and its effect on mushroom productivity

Source-separated food waste is increasingly being treated by means of hygienisation followed by anaerobic digestion. The fibrous digester residue (digestate) is a potential mushroom substrate, while heat from the biogas can provide steam for the cultivation process. Using bag experiments the present study explored digestate as a full substitute for chicken manure conventionally used in mushroom composts. After mixing, a rapid temperature development in the compost was stimulated by a small amount of chicken manure, as aerobic microbial seeding. Mechanical elimination of lumps was essential for full mycelial colonisation. Three straw digestate composts had Agaricus bisporus mushroom yields above 370 g kg⁻¹ substrate. The optimal compost water content was 600 g kg⁻¹ at inoculation, and high digestate content (up to 500 g kg⁻¹ by dry weight) did not affect yield for this species. High yields of A. subrufescens (200 g kg⁻¹) were related to drier composts of lower digestate content (more straw) and lower pH values at inoculation. Digestate successfully substituted chicken manure in straw composts without affecting mushroom yields for both species. There were no clear differences between straw digestate and control composts in terms of mushroom dry matter, size, nitrogen or ash content.

Phosphorus and Energy Recovery from Manure and Digestion Residues

Human and animal excrements, in particular manure, stand for a significant and undisputable source of plant nutrients and renewable energy. In Europe, only 36% of P-inputs to soils originate from primary resources (rock phosphate) whereas 63% come from animal and human excretions applied to cropland as manure, digestion residues and sewage sludge. Simultaneously these waste flows represent a potential hazard to human health and aquatic bodies because of pathogens and eutrophication. Management of these waste flows is far from being sustainable, in part due to the lack of efficient processing technologies. A cooperative InnoEnergy—EIT financed KIC Knowledge and Innovation Community—research project pursues development and demonstration of highly efficient technologies to overcome the constraints and to yield renewable phosphate fertilizers and energy from waste flows that may have a combined technical energy potential of 3,600 PJ/year and an annual phosphate recovery potential of 4.5–5.5 million tonnes (as P2O5) in Europe.

Comprehensive Two-Dimensional GC with TOF-MS Detection: Study of Pyrolytic Bio-Oil of Kraft Mill Residues

Brazil is a great manufacturer of Eucalyptus pulp and has experienced important improvements in the environmental management in the last decades. However, there are still opportunities for alternative uses of pulp mill residues, which may result in higher added value products. Qualitative and semi-quantitative characterizations of bio-oil composition of three pulp mill residues (Eucalyptus sawdust, digester residue and wastewater treatment sludge) were performed using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC×GC/TOF-MS). The best pyrolysis conditions achieved for the digester residue were applied to the other residues and similar bio-oils were obtained for sawdust and digester residue, while sludge rendered a more complex pyrolysate. The advantages of GC×GC/TOF-MS for this specific application are presented, as well as the potential of bio-oil components for important industrial applications.

Evaluation of energy digestibility of canola coproducts by in vitro analyses and characterization of fat digestion using spectroscopy1

In vitro methods did not accurately predict in vivo apparent total tract digestibility of energy for canola coproducts (r = -0.81; P = 0.002). We scanned 153 samples of digesta, feces, and in vitro digestion residues (ivR) on a Fourier transform midinfrared instrument with a single-reflection attenuated total reflectance attachment. The second derivative spectral net intensities of the carbonyl ester peak at 1745 cm(-1) and olefinic hydrocarbon (=C-H) peak at 3008 cm(-1) were both higher in ivR than in feces (3.83 × 10(-04) vs. 3.46 × 10(-05) and 7.92 × 10(-05) vs. 5.17 × 10(-06), respectively; P < 0.001), indicating poor enzymatic digestion of unsaturated fat. In conclusion, fat digestion of in vitro procedure for canola coproducts requires improvement to adequately mimic in vivo digestion in pigs.

Fluazuron-induced morphophysiological changes in the cuticle formation and midgut of Rhipicephalus sanguineus Latreille, 1806 (Acari: Ixodidae) nymphs

The present study demonstrated the effects of the arthropod growth regulator, fluazuron (Acatak®), in the formation of the integument and digestive processes of Rhipicephalus sanguineus nymphs fed on rabbits treated with different doses of this chemical acaricide. For this, three different doses of fluazuron (20, 40, or 80mg/kg) were applied "pour on" to the hosts (groups II, III, and IV), as well as distilled water to the control group. On the first day after treatment (24h), the hosts were artificially infested with R. sanguineus nymphs. After full engorgement (7days), the nymphs were removed, placed on labeled Petri dishes, and kept in biochemical oxygen demand incubator for 7days. The engorged nymphs were then taken for morphological, histochemical, and histological analyses. The results showed the occurrence of cytological, morphohistological, and histochemical alterations in the integument and midgut of nymphs from all the different treated groups. These alterations occurred at cuticular level in the subdivisions of the cuticle, related to the size of the digestive cells, amount of accumulated blood elements, and digestive residues, as well as the presence of vacuoles in the cytoplasm of the digestive cells. Thus, this study demonstrated that fluazuron acts on the integument and midgut cells of R. sanguineus nymphs fed on treated rabbits and pointed out the possibility of the use of this chemical-which is more specific, less toxic, and less harmful to the environment and nontarget organisms-in the control of R. sanguineus, at least in the nymphal stage of its biological cycle.

Structural Changes of High-Amylose Rice Starch Residues following in Vitro and in Vivo Digestion

High-amylose cereal starch has a great benefit on human health through its resistant starch content. In this paper, starches were isolated from mature grains of high-amylose transgenic rice line (TRS) and its wild-type rice cultivar Te-qing (TQ) and digested in vitro and in vivo. The structural changes of digestive starch residues were characterized using DSC, XRD, (13)C CP/MAS NMR, and ATR-FTIR. TQ starch was very susceptible to digestion; its residues following in vitro and in vivo digestion showed similar structural characteristics with TQ control starch, which suggested that both amorphous and crystalline structures were simultaneously digested. Both amorphous and the long-range order structures were also simultaneously hydrolyzed in TRS starch, but the short-range order (double helix) structure in the external region of TRS starch granule increased with increasing digestion time. The A-type polymorph of TRS C-type starch was hydrolyzed more rapidly than the B-type polymorph. These results suggested that B-type crystallinity and short-range order structure in the external region of starch granule made TRS starch resistant to digestion.