Mg Of Substrate Research Articles

The Effects of Wheat and Rice Straw as a Substrate on the Treatment of Reverse Osmosis Reject Wastewater in a Single Chamber Microbial Fuel Cell

AbstractThis work has examined the effect of cellulose based substrates such as rice straw and wheat straw on the treatment of Reverse osmosis (RO) reject wastewater in a single chamber microbial fuel cell (SCMFC). At a substrate concentration of 125 mg/L (125 mg of substrate in 1 L of RO reject wastewater), the two type of MFCs with rice straw and wheat straw as substrates were operated along with the third one as the control without any substrate. MFC with the wheat straw as the substrate outperformed the MFC with rice straw substrate in respect to maximum power density and total dissolved solid (TDS) removal of 127 mW/m2 and 71.88 percent, respectively. Performance of MFC with the three concentrations of 125, 250, and 500 mg/L of the chosen substrate (wheat straw) were compared. Substrate concentration of 125 mg/L was found to be the most effective. In SCMFCs formed for both the substrates, the ohmic losses were predominant, as shown by the polarization curves.

Preliminary in vitro screening of some spices and medicinal plants from Edo and Rivers States, Nigeria for reducing enteric methane production in ruminants

Methane gas produced by ruminants during feed fermentation contributed to global warming as well as poor efficiency of food utilization. Mitigating ruminal methane production through anti-microbial feed additive has serious health implications. A preliminary study of the potential of medicinal plants and spices from Edo and Rivers State, as possible replacement to antibiotic feed additives was carried out. Medicinal plants and spices were purposefully sampled, dried at 40oC, milled and 10 mg was added with 190 mg of substrate in a preweighed nylon incubation bags. Bags and their contents were incubated using 30 mL of buffered rumen liquor in 100 mL syringes following the standard procedure of in vitro fermentation. Variables monitored were 24h total gas volume, short chain fatty acids (SCFA) methane (CH4 ) gas, dry matter degradability (DMD) as well as some chemical, cell wall and anti-nutritive components. Results revealed that adding the medicinal plants and spices as feed additives did not depress gas production in most cases (19.5 – 29.50 mL, 17.75 – 30.00 mL and 12.00 – 29.00 mL for Edo medicinal plants, Edo spices and Rivers medicinal plants respectively) and also did not depress DMD (> 50%). Azadirachta indica stem reduced CH4 production mostly by 53.56% while Dennttia tripetala did by 47.69% among the Edo medicinal plants and spices, respectively. In Rivers State, Amaranthus spinosus gave the highest value of 60.33% CH4 reduction. In the same bracket of similar and good CH4 reduction potentials were Alstonia boonei leaves (49.06%), Newbouldia laevis root (41.50%), Euphorbia heterophyla (37.97%), Allium crispum (47.31%), Allium cepa (46.80%), Aframomum mueguata (46.54%), Capsicum annum (47.32%), Ageratum conyzoides (56.52%), Lagenaria breviflora (48.03%) and Centrosema molle (45.08%). All the medicinal plant and spices with potential for CH4 reduction had corresponding high SCFA values (0.46 – 0.65 Mmol) with tannin (%) and saponin (%) contents of 0.011 – 17.50 and 0.01 – 2.40 respectively. Conclusively, the medicinal plants and spices demonstrated good potentials for reducing rumen methane production in vitro and may be subjected to further in vivo studies.

Peptidases from Maclura Pomifera for Preparation of Food Protein Hydrolysates: Purification by Single-Step Chromatography and Characterization of Pomiferin I.

Our objective was to isolate peptidases from the latex of Maclura pomifera fruits and use them to hydrolyze food proteins, as well as to purify and characterize the main peptidase. Two partially purified proteolytic extracts were prepared by ethanol (EE) and acetone (AE) precipitation from an aqueous suspension of exuded fruit latex. EE was used to hydrolyze food proteins with a ratio of 0.19 caseinolytic units (Ucas) per mg of substrate. Different values of hydrolysis degree were observed for hydrolysates of egg white, soy protein isolate, and casein at 180min (9.3%, 31.1%, and 29.1%, respectively). AE was employed to purify a peptidase which exhibited an isoelectric point (pI) of 8.70 and whose abundance in AE was 28.3%. This enzyme was purified to homogeneity using a single-step procedure by cation-exchange chromatography, achieving an 8.1-fold purification and a yield of 16.7%. The peptidase was named pomiferin I and showed a molecular mass of 63,177.77Da. Kinetic constants (KM 0.84mM, Vmax 27.50 uM s-1, kcat 72.37s-1, and kcat/KM 86.15mM-1s-1) were determined employing N-α-carbobenzoxy-L-alanyl-p-nitrophenyl ester as substrate. Analysis by PMF showed only partial homology of pomiferin I with a serine peptidase from a species of the same family.

Effects of oregano essential oil on in vitro ruminal fermentation, methane production, and ruminal microbial community

Different inclusion rates of oregano essential oil (OEO) were investigated for their effects on ruminal in vitro fermentation parameters, total gas, methane production, and bacterial communities. Treatments were (1) control, 0 mg/L of OEO (CON); 13 mg/L (OEO1); 52 mg/L (OEO2); 91 mg/L (OEO3); and 130 mg/L (OEO4), each incubated with 150 mL of buffered rumen fluid and 1,200 mg of substrate for 24 h using the Ankom in vitro gas production system (Ankom Technology Corp., Fairport, NY). Treatment responses were statistically analyzed using polynomial contrasts. Digestibility of DM, NDF, and ADF increased quadratically with increasing OEO inclusion rates. Digestibility of DM and NDF were highest for OEO2, whereas ADF digestibility was highest for OEO3, compared with CON, with the remaining treatments being intermediate and similar. Ammonia nitrogen concentrations decreased from CON at a quadratic rate with increasing OEO inclusion rates, and OEO2 had the lowest concentration compared with the other groups. Total VFA, acetate, propionate, butyrate, valerate, and isovalerate concentrations linearly decreased with increasing OEO inclusion rates. Total gas production levels by CON and OEO4 were greater than those of OEO1, OEO2, and OEO3 in a quadratic response, and methane production linearly decreased from CON, compared with OEO4, at a decreasing rate with OEO inclusion rates. As determined by 16S rRNA sequencing, the α biodiversity of ruminal bacteria was similar among OEO inclusion rates. Increasing OEO inclusion rates linearly increased the relative abundance of Prevotella and Dialister bacteria. Several bacteria demonstrated different polynomial responses, whereas several bacteria were similar among increasing OEO inclusion rates. These results suggested that OEO supplementation can modify ruminal fermentation to alter VFA concentrations and reduce methane emissions by extensively altering the ruminal bacterial community, suggesting an optimal feeding rate for future animal studies of approximately 52 mg/L for mature ruminants.

Comparison of ethanol production from Gracilaria fisheri and Gracilaria tenuistipitata cultivated in aquaculture system in Thailand

Several species of seaweeds contain higher amounts of polysaccharides and low lignin. These species can be sources for bioethanol production and can be utilized for other biochemical production. In Thailand, large amounts of the red seaweeds Gracilaria fisheri and G. tenuistipitata can easily grow in effluents from aquaculture ponds and are used for wastewater treatment. This study was done to assess the potential substrates from these two Gracilaria species to produce ethanol. Different concentrations of substrate from each species (20–200 mg) were pretreated with 1 M H2SO4 at 95 °C for 150 min. The optimal pretreatment was 60 mg of substrate treated with 1 M H2SO4 at 95 °C for 150 min. This condition gave the highest amount of fermentable sugars in both Gracilaria species. Under these conditions, G. fisheri showed a higher catalytic efficiency (E = 5.2) than G. tenuistipitata (E = 4.1). Ethanol fermentation was performed by using the yeast strain Saccharomyces cerevisiae TISTR 5339. The ethanol produced from the G. tenuistipitata fermentation had the highest yield, producing 0.19 g ethanol g−1 glucose, whereas that of G. fisheri yielded 0.16 g ethanol g−1 glucose. This study suggests that the biomass of G. fisheri and G. tenuistipitata from a marine aquaculture system is a potential source for ethanol production.

Harnessing biosynthesis and quantitative NMR for late stage functionalization of lead molecules: Application to the M1 positive allosteric modulator (PAM) program

A facile method for late stage diversification of lead molecules for the M1 PAM program using biosynthesis is described. Liver microsomes from several species are screened to identify a high turnover system. Subsequent incubations using less than 1 mg of substrate generate nanomole quantities of drug metabolites that are purified, characterized by microcryoprobe NMR spectroscopy, and quantified to known concentrations to enable rapid biology testing. The late-stage diversification of lead compounds provides rapid SAR feedback to the medicinal chemistry design cycle.

Evaluation of three medicinal plants for methane production potential, fiber digestion and rumen fermentation in vitro

Effects of three selected medicinal plants on fermentation patterns and to evaluate their potential as antimethanogenic additives in ruminant feeds were studied. Effects of Nigella sativa, Rosmarinus officinalis and Zingiber officinale, which were added to the fermentation substrate as a dry powder, on ruminal fermentation, fibre digestion and methane production, were studied in vitro in batch cultures of mixed rumen microorganisms. Serum bottles containing 500 mg of substrate (a mixture of 500 mg of alfalfa hay, 400 mg of grass hay and 100 mg of barley grain per gram), 50 mg of the plant tested and 50 ml of buffered rumen fluid (10 ml sheep rumen fluid + 40 ml culture medium) were incubated at 39 ºC for 24 h. After incubation, gas and methane production, pH and volatile fatty acid (VFA) concentration in the incubation medium and dry matter and neutral detergent fibre disappearance were recorded. The amounts of methane produced after 24 hours of fermentation varied between 0.28 and 1.12mmol/gDM. A significant methane reduction was observed with monensin (75% less methane than control) and Nigella sativa (20% less methane than control) and no effect was observed with the other treatments. Further studies are warranted to confirm the antimethanogenic activity of Nigella sativa, establish a dose-response relationship, examine the stability in time of the effects, and test if the effects can be reproduced in vivo with animals.

Volatile fatty acids and methane production from browse species of Algerian arid and semi-arid areas

ABSTRACTThe objective of the study was to determine the in vitro rumen fermentation end-products of 10 browse species. Serum bottles containing 500 mg of substrate, 10 ml of sheep rumen fluid and 40 ml of buffered medium were incubated for 24 h. After incubation, pH, methane and volatile fatty acid (VFA) productions were recorded. There were differences among feedstuffs (p < .05) in pH and VFA production. Astragalus gombo resulted in the highest and Stipa tenacissima in the lowest VFA production. Gas production was highest for Medicago sativa and lowest for S. tenacissima. Methane production (ml/g DM incubated) varied greatly. The lowest methane production was for S. tenacissima and Arthrocnemum macrostachyum (11.4 and 11.5 ml/g DM, respectively) and the highest for M. sativa and A. gombo (25.8 and 22.7 ml/g DM, respectively). The differences among species shrank when methane was expressed per ml of total gas produced or per mol of VFA produced. This indicates that a lower methane production would be due to a low fermentability of the substrate incubated, rather than to a specific inhibitory effect on methanogenesis. Hence, the 10 browse species studied herein would show little potential for mitigating ruminal methane production.

On-line solid phase extraction of bismuth by FI–HG–AAS using l-proline immobilised on carbon nanotubes combined with factorial design

This study explores further the analytical capabilities of functionalised multiwalled carbon nanotubes with l-proline (pro-MWCNTs) for the reliable preconcentration and determination of Bi(III) in waters using an on-line flow injection hydride generation atomic absorption spectrometry (FI–HG–AAS) system. To avoid carbon nanoparticles aggregation, the preconcentration was carried out on a microcolumn filled with functionalised pro-MWCNTs and a low molecular weight polyethylene. The optimisation was performed by employing a full factorial design. The factors related to the optimisation process were the concentration of eluent and pH of the sample. The best performance was achieved packing the substrate in a microcolumn of 2.3mm (i.d)×25mm (pro-MWCNTs net length: 10mm), the pH was 7.0 and the concentration of the eluent (HCl) was 10% (v/v). Under optimal conditions, the adsorption capacity of the substrate was found to be 0.1mgg−1 reaching a preconcentration factor (PF) of 160. A detection limit (3σ) of 0.7ngL−1 was achieved, when using only 3.0mg of substrate. Interferences affecting Bi(III) signal were carefully studied. Precision, expressed as relative standard deviation (RSD) turned to be 1.5% at the 0.1μgL−1 level (n=10). Accuracy test for the entire analytical procedure was performed by means of the Standard Reference Material (SRM) NIST 1643e (trace elements in water) and results were in good agreement with the certified values. The system was evaluated for quantitative determination of Bi(III) in different categories of waters.

Effect of essential oils extracted from Satureja calamintha, Mentha pulegium and Juniperus phoenicea on in vitro methanogenesis and fermentation traits of vetch-oat hay

The impact of inclusion of essential oils (EO) extracted from Juniperus phoenicea, Satureja calamintha and Mentha pulegium at three levels: 0, 1.66, 3.33 and 6.66 μl/ml of incubation medium, on methane production and rumen fermentation traits of vetch-oat hay was studied in in vitro gas production test, using 200 mg of substrate in a 60 ml graduated syringes. Gas production was recorded at 3, 6, 9, 24, 48, 72 and 96 h. Methane was measured at 3, 24 and 96 h, while pH and ammonia N were analyzed just at 24 h of incubation. At 24 h of fermentation, all doses of EO reduced significantly total gas and methane production (P < 0.05). At the highest concentration and after 24 h, methanogenesis was decreased by 60.98, 57.70 and 64.64% for J. phoenicea, M. pulegium and S. calamintha, respectively. This effect was more pronounced at the end of fermentation (96 h) where reduction in methane production was superior to 72%. However, addition of EO increased pH and decreased significantly ammonia concentration, mainly, for high EO concentrations. The results indicate that these EO had a potential to reduce methanogenesis in the rumen, but further in vitro and in vivo trials are required to search optimum dose which reduce methane production without adversely changing dietary fermentation and rumen function. Key words: Methane, ammonia, essential oils, Satureja calamintha (Calament), Mentha pulegium (fliou, Menthe pouliot), Juniperus phoenicea (Arar, Genevrier), in vitro gas production test

Effects of monensin on the chemical composition of the liquid associated microbial fraction in an in vitro rumen fermentation system

The hypothesis of this study was that monensin alters chemical composition of liquid associated rumen microbes. Furthermore, this study generates information on the chemical composition of rumen bacteria as affected by a ionophore by analyzing different parameters within the same experiment. Monensin at 5 and 8μM was incubated with 380mg of substrate (hay:concentrate 70:30 w/w) for 24h in an in vitro gas production system. Monensin elicited no effects on nitrogen and true protein contents of the liquid associated microbial fraction, but sugar content and carbon did change on addition on monensin. Ratio of crude protein to purine bases decreased on adding monensin. True dry matter digestibility and short chain fatty acids production decreased on addition of monensin. Acetate, butyrate and valerate proportions decreased, whereas propionate and branched-chain fatty acid proportions increased. The change in acetate to propionate ratio concurs with the increase in the efficiency of microbial protein synthesis and the decrease in methane production. Results suggest that: monensin influenced the chemical composition of the liquid associated microbial fraction in vitro, and the changed ratio of crude protein to purine bases may lead to under- or over-estimations of microbial protein synthesis when purine derivatives are used as markers in the presence of monensin.

Vegetable oil soapstocks reduce methane production and modify ruminal fermentation

Four soapstocks from the refinery vegetable oil industry (SSpalm, SSoliv, SSsoyb and SSsunf (RIOSA, Baeza-Linares, Spain), from processing of palm, olive, sunflower, and soybean oils, respectively) and a mixture of lauric and miristic acids (4:1, LMA) added to diets with different forage proportions (50, 150 and 250g barley straw/kg diet; F5, F15 and F25 diets, respectively) were examined to assess their potential to modify ruminal fermentation in vitro, in particular CH4 production. Serum bottles containing 400mg of substrate (F5, F15, F25 diets) including 30 or 60g/kg of the materials and 50ml of buffered rumen fluid were incubated at 39°C for 24h. After incubation, gas and CH4 production, pH and volatile fatty acid (VFA) concentrations in the incubation medium were measured. All materials linearly decreased gas production (P<0.05), and SSoliv, SSsoyb and SSsunf reduced CH4 production (P<0.05) and methane produced per mol of total VFA formed (P<0.05), and LMA also reduced CH4 proportion in the gas (P<0.05), whereas SSpalm tended to decrease it. LMA linearly (P<0.05) decreased acetate production and the acetate to propionate ratio, and raised the propionate molar proportion and pH (P<0.05). SSoliv and SSsoyb caused a linear (P<0.05) decline in acetate, and rise in propionate, molar proportions, thus decreasing the acetate to propionate ratio (P<0.05), whereas SSsunf tended to have the same effects (P<0.10). As the forage proportion increased, CH4 and acetate proportion, acetate to propionate ratio and final pH increased, while gas, VFA (individual and total) and CH4 production, and propionate and butyrate molar proportions, decreased. Soapstocks, especially SSsoyb and SSsunf, are promising dietary alternatives to depress ruminal methanogenesis.

Effect of Mentha piperita L. on in vitro rumen methanogenesis and fermentation

The aim of this study was to evaluate the effect of Mentha piperita L. (MP) dried leaves on the in vitro rumen methanogenesis and fermentation. It was found that after 24 hours of incubations, addition of 16.34 and 23.35 mg of MP to the 233.3 mg of substrate significantly decreased methane emission by 41.52 and 15.51%, respectively. Simultaneously, the MP supplementation exerted no effect on the dry matter digestibility and volatile fatty acid profile. Addition of MP to the ruminants' diet inhibits the methane production without altering the basic parameters of rumen fermentation.

A Selective Intramolecular Transacylation of Taxoids Accompanying with the Oxetane Ring Opening

A selective intramolecular transacylation from C-4 to C-5 of taxoids, which occurred simultaneously with the oxetane D-ring opening and was promoted by TiCl4, was presented. The optimal condition was found to be treatment of substrates in double dose of dichloromethane (per mg of substrate dissolved in 2 mL DCM) with 1 eq of TiCl4 at 25°C for 10 min.

Chemical composition of rumen microbial fraction and fermentation parameters as affected by tannins and saponins using an in vitro rumen fermentation system

Castro-Montoya, J. M., Makkar, H. P. S. and Becker, K. 2011. Chemical composition of rumen microbial fraction and fermentation parameters as affected by tannins and saponins using an in vitro rumen fermentation system. Can. J. Anim. Sci. 91: 433–448. Post-rumen chemical composition of the microbial fraction is one of the factors that determines the nutrients absorbed and available for maintenance and production of the animal. The hypothesis was that tannins and saponins alter chemical composition of rumen microbes and fermentation parameters in the rumen. Purified quebracho, mimosa, chestnut and sumach tannins; and quillaja and gypsophilla saponins were incubated with 380 mg of substrate (hay:concentrate 70:30 wt/wt) for 24 h in an in vitro gas production system at concentrations from 0.25 to 1.25 mg mL−1. Saponins increased N and reduced sugar contents of the liquid-associated microbes. The ratio of crude protein to purine bases significantly increased on adding sumach and chestnut tannins and decreased on the addition of quebracho and mimosa tannins. Quebracho, mimosa and chestnut tannins reduced total short-chain fatty acid production. The acetate:propionate ratio decreased for all additives. Results suggest that in vitro (a) depending on the source and the concentration, tannins would have an effect on the nitrogen and sugar contents of the liquid associated microbes, (b) saponins are likely to increase N and reduce sugar contents of rumen liquid associated microbes, and (c) estimation of microbial protein synthesis based on purine bases may lead to under- or over-estimations in the presence of tannins and saponins. In vivo studies are required to validate these results.

An Insecticidal GroEL Protein with Chitin Binding Activity from Xenorhabdus nematophila

Xenorhabdus nematophila secretes insecticidal proteins to kill its larval prey. We have isolated an approximately 58-kDa GroEL homolog, secreted in the culture medium through outer membrane vesicles. The protein was orally insecticidal to the major crop pest Helicoverpa armigera with an LC50 of approximately 3.6 microg/g diet. For optimal insecticidal activity all three domains of the protein, apical, intermediate, and equatorial, were necessary. The apical domain alone was able to bind to the larval gut membranes and manifest low level insecticidal activity. At equimolar concentrations, the apical domain contained approximately one-third and the apical-intermediate domain approximately one-half bioactivity of that of the full-length protein. Interaction of the protein with the larval gut membrane was specifically inhibited by N-acetylglucosamine and chito-oligosaccharides. Treatment of the larval gut membranes with chitinase abolished protein binding. Based on the three-dimensional structural model, mutational analysis demonstrated that surface-exposed residues Thr-347 and Ser-356 in the apical domain were crucial for both binding to the gut epithelium and insecticidal activity. Double mutant T347A,S356A was 80% less toxic (p < 0.001) than the wild type protein. The GroEL homolog showed alpha-chitin binding activity with Kd approximately 0.64 microm and Bmax approximately 4.68 micromol/g chitin. The variation in chitin binding activity of the mutant proteins was in good agreement with membrane binding characteristics and insecticidal activity. The less toxic double mutant XnGroEL showed an approximately 8-fold increase of Kd in chitin binding assay. Our results demonstrate that X. nematophila secretes an insecticidal GroEL protein with chitin binding activity.

In vitro screening of the potential of numerous plant species as antimethanogenic feed additives for ruminants

A screening experiment was conducted to evaluate the potential of 450 plant species as antimethanogenic additives in ruminant feeds. Effects of addition of these plants, which were incorporated to the fermentation substrate as a dry powder, on ruminal fermentation, fibre digestion and methane production were studied in vitro in batch cultures of mixed rumen microorganisms. Serum bottles containing 500 mg of substrate (500 g alfalfa hay/kg, 400 g grass hay/kg and 100 g barley grain), 50 mg of the plant additive tested and 50 ml of buffered rumen fluid (10 ml sheep rumen fluid + 40 ml culture medium) were incubated at 39 °C for 24 h. After incubation, gas and methane production, pH and volatile fatty acid (VFA) concentration in the incubation medium and dry matter and neutral detergent fibre disappearance were recorded. Of the 450 samples tested, 35 decreased methane production by more than 15% versus those with corresponding control cultures and, with 6 of these plant additives, the depression in methane production was more than 25%, with no adverse effects on digestibility, total gas and VFA production. With these six samples, incubations were repeated to confirm their effects on methane production in vitro. Some candidates, in particular Rheum nobile and Carduus pycnocephalus, consistently decreased methane production without adversely affecting other parameters of the rumen fermentation.

Using an in vitro gas production technique to examine feed additives: Effects of correcting values for different blanks

Several in vitro experiments were conducted to determine effects of additives on rate and extent of gas production when several substrates were incubated in batch cultures of mixed rumen microorganisms. In all experiments, 500 mg of substrate was incubated with 50 ml of buffered rumen fluid at 39 °C and gas production was measured at 2, 4, 6, 9, 12, 16, 21, 26, 31, 36, 48, 60, 72, 96 and 120 h. In experiments involving organic acids, three substrates differing in their forage:concentrate ratio (80:20 (F80), 50:50 (F50) and 20:80 (F20)) were incubated without additives, but in the presence of two doses (4 and 8 mM) of fumarate or malate. In the experiment with fibrolytic enzymes, samples of four tropical forages were incubated without additives and with three different enzyme solutions (cellulase, xylanase, and a 1:1 mixture of cellulase and xylanase) added at a rate of 20 IU/g dry matter forage. Blanks (i.e., bottles without sample) containing only buffered rumen fluid (B0) or buffered rumen fluid plus the corresponding dose of each additive (BA) were included for correction. Gas production values were fitted to the exponential model: gas = A(1 − e (− c( t − lag)) ), and the average gas production rate (AGPR; ml gas/h) and organic matter effective degradability (OMED) were calculated. There were no blank×substrate or blank×additive interactions in any experiment. When B0 were used to correct gas production values, adding malate linearly increased ( P<0.05) parameters A (asymptotic gas production) and AGPR for all substrates, but no differences due to malate addition occurred for any substrate when gas values were corrected for BA. Adding fumarate to all substrates linearly increased ( P<0.05) parameters A, c (fractional rate of gas production) and AGPR when B0 was used for calculations, but it only tended ( P<0.10) to linearly increase AGFR for substrate F80 and asymptotic gas production for substrate F50 when using BA for calculations. In the experiment with enzymes, there were only subtle differences between results obtained using B0 and BA for correcting gas values. With both blanks, treatment of forages with cellulase and the cellulase:xylanase mixture decreased ( P<0.05) lag and increased ( P<0.05) OMED for all forages. Results demonstrate that using different blanks for correction purposes can produce different calculated effects between treatments, and therefore, can change interpretation of results, but this effect depends on the type of additives examined.

The effects of proanthocyanidins from Calliandra calothyrsus and the alkaloid sparteine on in vitro fiber digestion

Tropical legumes accumulate anti-nutritive compounds whose impact on the nutritive value of livestock feeds is difficult to evaluate. Many studies have focused on the effects of a single compound while animals simultaneously cope with several. In vitro measurements of gas production were used to study the roles of proanthocyanidins (PA) and alkaloids (AL) on nutrient use by ruminants. Napier grass ( Pennisetum purpureum (Schum) cv Bana: NG) and its isolated NDF (iNDF) were incubated with four levels (0, 0.14, 0.28 and 0.42 mg ml −1) of PA from Calliandra calothyrsus (Meissner), a tropical leguminous shrub, and four levels (0, 0.25, 0.50, 0.75 mg ml −1) of sparteine, a quinolizidine alkaloid. Coefficient of neutral detergent fiber digestibility of intact NG was lower ( P < 0.001) than that of the iNDF (0.431 versus 0.598) and the tannin–alkaloid interaction was not significant. Sparteine depressed NDF digestibility by 0.054 and PA by 0.115. Neutral detergent fiber digestibility of both iNDF and intact NG was inversely related to PA ( y = −0.0424 x + 0.705; R 2 = 0.99 and y = −0.0326 x + 0.513; R 2 = 0.98, respectively). Sparteine did not affect ( P > 0.05) final gas volume or its rate of production. Proanthocyanidins at 0.42 mg ml −1 decreased final gas volume from 13.4 ml of gas per 100 mg of substrate (control) to 11.4 ml and the rate of gas production from 0.053 to 0.037 h −1. However, there was an interaction ( P < 0.01) between AL and PA when rate of gas production was the dependent variable. Proanthocyanidins increased lag time ( P < 0.05) in NDF fermentations linearly ( y = 1.92 x + 2.2; R 2 = 0.9942) while sparteine had no effect on lag ( P > 0.05). Microbial protein synthesis estimated from purine yield was suppressed ( P < 0.01) by AL (from 34.1 to 24.7 μg), but low levels of PA (0.14 mg ml −1) increased purine yield compared to the control and higher PA levels. Simulations with the Cornell Net Carbohydrate and Protein System (CNCPS) showed that PA decreased rate of NDF digestion, thus reducing metabolizable energy and protein allowable milk. The effects of tannins, alkaloids and other secondary compounds should be included in ration formulation models.

Oxygen uptake during mineralization of humic substances from Infernão Lagoon (São Paulo, Brazil)

Assays were carried out to evaluate the dissolved oxygen uptake resulting from mineralization of humic substances (fulvic acid (FA) and humic acid (HA)) from different sources: sediment, dissolved organic matter (DOM) of 120-day decomposed aquatic macrophyte (Scirpus cubensis and Cabomba piauhyensis), and lagoon DOM. The experiments were also aimed at estimating the oxygen uptake coefficient of the mineralization. About 20-30 mg of substrate were added to 1.1 liters of water from Infernão Lagoon (21 degrees 33' to 21 degrees 37'S; 47 degrees 45' to 47 degrees 51'W). The solutions were aerated and the dissolved oxygen (DO) was monitored during 40 days. Dissolved organic carbon (DOC) and particulate organic carbon (POC) were estimated after 80 days of the experiment. Anaerobic processes were avoided by aerating the solutions. The results were fitted to a first-order kinetics model, from which the uptake of oxygen parameters was obtained. Oxygen consumption (OC) ranged from 4.24 mg L(-1) (HA--S. cubensis) to 33.76 mg L(-1) (FA--sediment). The highest deoxygenation coefficient (kD) was observed during mineralization of FA--DOM (0.299 day(-1)), followed in decreasing order by FA--S. cubensis, HA--sediment, HA--S. cubensis, FA --sediment, and FA--C. piauhyensis (0.282; 0.255; 0.178; 0.130, and 0.123 day(-1), respectively). The carbon analyses indicated that the FA and HA samples at the end of the experiment presented a decay that varied from 15.23% to 42.35% and that the FA and HA conversions into POC were relatively low (from 0.76% to 3.94%).