1,721,005 research outputs found
Manometric monitoring of biological denitrification
Get PDFA simple, automated manometric method is here discussed and applied to perform batch experiments for the stoichiometric and kinetic characterization of biological denitrification. The main strength of the proposed methodology is that it requires simple instrumentation, which is usually available in wastewater treatment plant laboratories, being it used in BOD and in BMP tests. The experimental setup consists of a glass bottle, a mixing and termostated system and a manometric bottle-head which can measure and log the overpressure that is caused by denitrified N2. At first, tests were conducted to determine the repeatability of the method; they were performed under low Food-to-Biomass ratio and with both endogenous and externally dosed carbon sources. Later, experimental procedures were performed to assess (1) the anoxic growth yield, (2) the endogenous anoxic decay rate; (3) the anoxic growth rate on acetate; (4) the fraction of anoxic active biomass in the sludge sample. Sludge samples for all these tests were taken from two WWTPs and 6 to 10 replicates were performed each time. Results indicated that the testing procedures is well repeatable and reliable and resulting estimates were within reported literature values
Valorizzazione del siero di caseificazione producendo energia. In: Biogas da agrozootecnia e agroindustria
No full textEnzymatic and metabolic activities in four anaerobic sludges and their impact on methane production from ensiled sorghum forage.
No full textBMP tests were used in order to evaluate the anaerobic digestibility of ensiled sorghum forage. Being a
batch test, the BMP assay is strongly dependent on initial conditions especially on the nature of the
anaerobic sludge inoculum. The inoculum selection may have a relevant impact on both biomethanization
rate an final BMP value after a selected operative digestion time. These aspects can make BMP values
difficult to compare. To explain the origin of the observed differences on methane production, BMP tests
were run on sorghum forage using four inocula (urban, agricultural, mixture of agricultural and urban,
granular sludge) and metabolic and enzymatic activities were measured during the course of BMP tests.
Results indicate that lower differences were observed in terms of BMP values with a slight higher value
when agricultural sludge was used as inoculum, possibly due to the adaptation of the bacterial consortium to
similar agricultural wastes. Significant differences can be observed among different inocula, in terms of
biomethanization rate. The fastest biomethanization occurred when using the urban sludge while the slowest
one was obtained from the agricultural sludge, in agreement with the observed hydrolytic activities.
Differences on the hydrolytic and enzymatic activities are also discussed
Zymomonas mobilis: biomass production and use as a dough leavening agent
Get PDFZymomonas mobilis ferments only glucose, fructose and sucrose via the Entner-Doudoroff pathway, providing an equimolar mixture of ethanol and CO2 and theoretically, as for Saccharomyces cerevisiae, the gas evolved can be used to leaven a dough. However, the capability of Z. mobilis to produce CO2 has rarely been exploited. In the present study we first evaluated the growing performance of two Z. mobilis strains (DSMZ 424 and 3580) in a culture medium lacking yeast extract, with added glucose or fructose (20 and 50 g/L) comparatively; the results demonstrated that biomass yield is 50 % higher with glucose. The best conditions were up-scaled, obtaining a biomass yield of 1.3–1.4 g dcw/L in a 14-L fermenter. Leavening trials performed in a model system with the biomass collected from fermenters after 9 or 16 h incubation evidenced that Z. mobilis can leaven a model dough as S. cerevisiae does, and showing a CO2 production rate (9–11 mL g dcw−1 min−1) statistically higher than that of S. cerevisiae (6–7 mL g dcw−1 min−1), especially when using 9-h-grown biomass. Bakery products leavened with Z. mobilis could thus be available to people with adverse responses to the ingestion of bakery food, providing innovation in the area of yeast-free leavened baked goods
Effect of particle size on alkaline pretreatment and methane production of ensiled sorghum forage.
No full textResidual and dedicated energy crops, such as sorghum, are suitable substrates for anaerobic
digestion in agricultural biogas plants. However, their complex structure justifies the use of a
pretreatment to improve their anaerobic biodegradability. Thus, the aim of this study was to
investigate the impact of particle size reduction on structural changes and methane production
from ensiled sorghum forage, with and without the addition of sodium hydroxide. Sorghum
samples were ground into particles with mean diameters of 994, 471, 269 and 169 μm. Milled
samples with 471 and 169 μm particle sizes were soaked in a NaOH solution at 10%
gNaOH/gTS dosage and maintained at 55°C for 12 h. BMP tests were performed on all
samples. All results are discussed both in terms of specific methane production and kinetic
constants. The main conclusion is that milling did not improve methane production (275.3±
3.5 mLCH4/gVS) nor kinetic constants (0.11±0.01 d-1) between 994 and 169 μm. On the
contrary, by adding sodium hydroxide, an increase in both methane yield (324.5±0.7
mLCH4/gVS) and kinetic constants (0.16 ± 0.00 d-1) was observed, but these results were not
influenced by the particle size. Chemical and infra red spectroscopy (FTIR) analysis were
performed to characterize the samples and explain these results
Comparative study of different pretreatments to enchance methane production of sorghum forage.
No full textSorghum represents a suitable substrate for anaerobic digestion in agricultural biogas plants. As lignocellulosic
substrate, the anaerobic biodegradability of sorghum depends on its content of cellulose, hemicellulose and
lignin. Cellulose and hemicelluloses are generally degradable under anaerobic conditions; nevertheless, lignin
acts as a physical barrier, preventing their degradation. Therefore, pretreatments are needed to improve the accessibility of holocellulose and thereafter increase the methane potential of sorghum. The aim of this study was
to compare the effects of different pretreatments on methane production of ensiled sorghum forage.
Ensiled sorghum forage, used for animal feed, was collected from a farm near Cremona (Italy). After collection,
it was dried and stored in air-tight containers prior to use. Mechanical pretreatment was performed by using a
cutting mill (Retsch) with a 2, 1, 0.5 and 0.25 mm screens. Sorghum samples were ground into particles with
mean diameters of 994, 471, 269 and 169 μm. Sodium hydroxide pretreatment tests were conducted by soaking
samples (0.5–1.5 mm particle sizes) in a NaOH solution at 40°C for 24 h, at different NaOH dosages (1 and 10 g
NaOH/100gTS). Thermal pretreatment tests were performed using a cylindrical steel tank with a volume of 6.2
L. Sample was introduced in the tank with tap water (6 g H2O/gTS), heated to reach the desired temperature (at
100°C and 160°C) and maintained at this condition for 30 min. After alkaline and thermal pretreatments, sam-70
ples were filtered through a sieve of 0.8 mm of pore size. The sieve-separated solid and liquid fractions were
taken for compositional analysis. Enzymatic pretreatment was performed employing a mixture of the following
commercial preparations: Agazym BGL (Garzanti Specialties) and Primafast 200 (Genencor Inc.). BGL was found
to contain 120.3 ± 5.9 mg protein /ml, 235.7 ± 24.3 IU/ml endoglucanase activity and 126.5 ± 10.6 IU/ml
xylanase. Primafast is a highly concentrated preparation containing 167.0 ± 9.5 mg protein/ml, with 2063.4 ±
0,8 IU/ml endoglucanase and 282.8 ± 5.7 IU/ml xylanase. Enzymes were added at a final concentration of up
to 0.40 and 0.12 ml/gTS respectively, then H2O was added (3 ml/gTS), pH set at 5.0 and samples incubated at
50 °C for up to 72 h. Sugars were determined by HPLC using a Refractive Index (RI) detector. BMP tests were
performed in duplicate under mesophilic conditions (35°C). The substrate to inoculum ratio was 1 gVS/gVS.
NaOH pretreatment and combined NaOH and enzymatic pretreatment resulted in the highest methane yield
increase. At the highest NaOH dosage, the specific methane production of sorghum increased by 26% and up to
35-36%, by a combined NaOH and enzymatic pretreatment. A reduction of particle sizes, within the range studied, didn’t improve significantly the maximum methane production of ensiled sorghum forage. No significant
effect of thermal and enzymatic pretreatment were also observed
Alkaline pretreatment of sorghum and wheat straw for increasing methane production
No full textThe aim of this study was to determine the effect of alkaline pretreatment on fiber composition,biodegradability and methane production rate of sorghum forage and wheat straw. Samples were treated at 40 °C for 24 h with a sodium hydroxide solution. The specific dosages were 1, 3 and 10gNaOH/100gTS. By increasing the alkaline dosage, a reduction in the total fiber content and an increase in COD solubilization is observed. Total sugars content increased up to five times at the highest alkaline dosage with respect to control samples, proving that alkali pretreatment improves substrate swelling and hydrolysis of hemicellulose.
Biochemical methane production tests showed that the chemical pretreatment increased both the ultimate anaerobic biodegradability and the methanization rate. The ultimate biodegradability was
increased from 66 to 86% for sorghum and from 56 to 72% for wheat straw. The first order kinetic constant for methane production was increased by 33% (from 0.21 to 0.28 d-1) for sorghum and by 170% (from 0.10 to 0.27 d-1) for wheat straw
Sodium hydroxide pretreatment of ensiled sorghum forage and wheat straw to increase methane production
No full textThe aim of this study was to determine the effect of sodium hydroxide pretreatment on the chemical
composition and the methane production of ensiled sorghum forage and wheat straw. NaOH
pretreatment was conducted in closed bottles, at 40 WC for 24 h. Samples were soaked in a NaOH
solution at different dosages (expressed in terms of total solids (TS) content) of 1 and 10% gNaOH/gTS,
with a TS concentration of 160 gTS/L. At the highest NaOH dosage the reduction of cellulose,
hemicelluloses and lignin was 31, 66 and 44%, and 13, 45 and 3% for sorghum and wheat straw,
respectively. The concentration of soluble chemical oxygen demand (CODs) in the liquid phase after
the pretreatment was also improved both for wheat straw and sorghum (up to 24 and 33%,
respectively). Total sugars content increased up to five times at 10% gNaOH/gTS with respect to
control samples, suggesting that NaOH pretreatment improves the hydrolysis of cellulose and
hemicelluloses. The Biochemical Methane Potential (BMP) tests showed that the NaOH pretreatment
favoured the anaerobic degradability of both substrates. At 1 and 10% NaOH dosages, the methane
production increased from 14 to 31% for ensiled sorghum forage and from 17 to 47% for wheat straw.
The first order kinetic constant increased up to 65% for sorghum and up to 163% for wheat straw
Impact of different types of pre-treatment on methane production of two agricultural substrates.
No full textThe aim of this study was to compare the effects of different types of pretreatment (thermal,
alkaline, enzymatic and combination of them) on chemical composition and anaerobic
biodegradability of ensiled sorghum forage and wheat straw. All the pre-treatments tested led to a
solubilisation of fibrous fractions for both substrates. The highest lignin reduction, compared to
untreated samples, was found at 100°C with 10% NaOH dosage (53% and 72% for wheat straw
and sorghum, respectively). Under this pre-treatment condition a high hemicelluloses reduction
yield was also found (63% for both substrates). The highest increase in methane yield (up to 29%),
compared to the untreated substrate was observed at 40°C with 10% NaOH for sorghum. As for
wheat straw, significant increases in methane yield were observed at 40°C with 10% NaOH (49%),
at 100°C with 1-10% NaOH (55 and 75%, respectively), and after enzymatic pretreatment (40%)
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