determining feed quality for ruminants using in vitro gas ... · pressure sensors report ... times...
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Determining feed quality for ruminants using in vitro gas production technique.
1. Building an anaerobic fermentation chamber
L. O. Tedeschi*, P. Schofield#, A. N. Pell#
* Texas A&M University, College Station, TX 77845‐2471
# Cornell University, Ithaca, NY 14853
Introduction
There are several techniques to determine the fermentation pattern of feeds through incubation in rumen fluid. The in vivo and in situ techniques are known for their laborious and expensive methods, large variation, and difficult to standardize (Huntington and Givens, 1995). Others have provided extensively discussion of the advantages and drawbacks of in situ techniques (Nocek, 1988; Vanzant et al., 1998).
Techniques that use in vitro incubation with rumen fluid have been described and used to determine the fermentation pattern of feeds (Goering and Van Soest, 1970; Tilley and Terry, 1963) mainly because their ease of use and cost. The in vitro technique has its own limitations. The single major factor affecting the pattern of fermentation is likely to be the inoculum because of the intrinsic variability of the rumen fluid and the collection schedule. Other factors include diets fed to donor animals and species of donor animal (Rymer et al., 2005). The dietary fiber in the donor’s ration may also affect the in vitro dry matter (DM) digestibility, even when chemical composition of the diets is similar (Cherney et al., 1993). When feedstuffs are incubated with buffered rumen fluid, the degraded carbohydrate fraction may either contribute to CO2, CH4, and volatile fatty acids (VFA: acetic, propionic, and butyric) or be incorporated into microbial biomass (Rymer et al., 2005). Direct comparisons between in situ and in vitro methods have been conducted by Varel and Kreikemeier (1995). These authors reported that on average lag time was 3.5 h less, fractional rate of degradation was 3%/h faster, and extent was 6% greater for the in situ than for the in vitro method for determining fiber digestion kinetics. Therefore, one could use these biases in adjusting in vitro estimates for in situ values.
Pell and Schofield (1993) developed a computerized gas production system in which individual pressure sensors transmitted data to an IBM‐PC via an analog‐to‐digital converted (ADC) card. This automated process could generate several data points for each sample within an acceptable fermentation period. Their system included an incubator with a multiplace stirrer, pressure sensors attached to the incubation 50‐ml Wheaton flasks, and ADC card, a computer with the Microsoft Windows 3.1, and the Atlantis Software for Win 3.1 as shown in Figure 1. Their system was able to read 16 channels at a time. More information was described by Schofield (1996). Previous analyses have indicated that flasks volume have no effects on the in vitro digestibility of DM and neutral detergent fiber (NDF) (Sayre and Van Soest, 1972), and fermentation pattern and VFA profile (Schofield and Pell, 1995), but they might capture mode information of the fermentation process than small flaks (Schofield and Pell, 1995) and the size of the error is proportionally reduced. There has been some discussion
1
about the impact of the pressure that builds up inside the flasks on microbial growth when gas is not released (Rymer et al., 2005).
The objective of this paper is to describe the development of a fermentation chamber similar to that described by Pell and Schofield (1993) except it was designed to contain more and larger fermentation flasks. The second objective is to build a fermentation chamber in which it would be possible to record other measurements inside of the Wheaton flasks simultaneously in the future, such as methane and VFA.
Material and Methods
Electronic circuit to supply power to pressure sensor. The sensors used by Pell and Schofield (1993), 185PC15DT from Micro Switch (Freeport, IL) was not available when building our fermentation chamber. Therefore, the sensor PX40‐15G5V (Omega Engineering Inc., Stamford, CT, 06906‐0669, http://www.omega.com) (Figure 2A) was used. This sensor measures 0 to 15 psi (1 atm), requires an excitation of 5 V with 10 mA, and returns a voltage signal of 0.5 ± 0.11 V at 0 psi and 4.0 ± 0.11 V. During the anaerobic fermentation, there is no release of gas that is produced through fermentation and the pressure sensors report the accumulated gas. There are other systems that release the pressure when it reaches a certain value (Cone et al., 1996). An electronic circuit was build onto a printed circuit board (PCB) to convert 12 V to 5 V as shown in Figure 3. In Figure 3, Vin is 12 V and Vout is 5 V. The resistance R2 is the internal resistance of the pressure sensor PX40‐15G5V, which was measured to be 3.6 kΩ. A fixed resistance of 3.6 kΩ was used for R1. Equation [1] shows the calculation of the total resistance.
1 2 3.6 3.6 1.81 2 3.6 3.6T
R RR kR R× ×
= = =+ +
Ω [1]
Therefore, the Rv that would satisfy the Vin and Vout, given the total resistance of 1.8 kΩ is 2.5Ω (Equation [2]).
1.81.8
1.85 121.8
2.5
Vout VinRv
RvRv k
⎛ ⎞= ×⎜ ⎟+⎝ ⎠⎛ ⎞= ×⎜ ⎟+⎝ ⎠
∴ = Ω [2]
Electronic circuit to process the signal from the pressure sensor. The ADC used to convert analog signals from the pressure sensors to a digital signal to be read by a computer was a card with USB connectors (USB ADC‐11; PicoTech, Cambridgeshire, UK; http://www.picotech.com) (Figure 2B). This USB ADC‐11 has an input of 0 to 2.5 V. However, the pressure sensor PX40‐15G5V (Figure 2A) has an output of 0.5 to 4 V. Therefore, a voltage divider as shown in Figure 2C was built to provide 2.5 V at the maximum output of the pressure sensor. The R1 of the USB ADC‐11 is 1 MΩ. Therefore, the total resistance (3.58 kΩ) was calculated as shown in Equation [3].
2
1 2 1000 3.6 3.581 2 1000 3.6T
R RR kR R× ×
= = =+ +
Ω [3]
Therefore, the Rv that would satisfy the Vin and Vout, given the total resistance of 3.58 kΩ is 2.148 kΩ (Equation [4]).
3.583.58
3.582.5 43.58
2.148
⎛ ⎞= ×⎜ ⎟+⎝ ⎠⎛ ⎞= ×⎜ +⎝ ⎠
⎟
∴ = Ω
Vout VinRv
RvRv k
[4]
Figure 2C shows the PCB with 22 voltage dividers, 11 to convert 12 V into 5 V (left) and 11 to convert 4 V into 2.5 V (right). The pressure signal, after being divided, was connected to a terminal board (Figure 2C) (PicoTech, Cambridgeshire, UK; http://www.picotech.com) and then connected to the ADC (Figure 2B) using a RS 25 cable.
Incubation Chamber. An wood incubation chamber was built to allow control of ideal temperature for anaerobic fermentation (about 39 oC) as shown in Figure 4. The source of heat was two 100‐W lamps and two fans to homogeneously dissipate the heat inside the chamber. The 125‐ml Wheaton bottles are placed on top of plywood (Figure 4C); the magnets are located underneath the plywood; and the rotors are attached underneath a second plywood to rotate the magnets so the stirrers inside the Wheaton bottles can agitate the fluid as the rotors turn the magnets (Figure 4D).
Software. The PicoLog is the software developed and recommended by PicoTech. The fermentation chamber shown in Figure 4 uses PicoLog to record the pressure signals from the ADC. The version of the PicoLog is 5.16.2.
Macro and micro solutions. The phosphate‐bicarbonate medium and reducing solution for macro and micro solutions for in vitro anaerobic fermentation was based on Goering and Van Soest (1970). The macro solution is made by mixing the ingredients listed in Table 1 in 1 L of distilled water. The ingredients for the micro solution is shown in Table 1; mix all the ingredients and add distilled water to volumetrically complete 100 ml. Alternatively, the micro solution proposed by Schaefer et al. (1980) could also be used. The formula is shown in Table 2; the ingredients are mixed in 1 L of distilled water. Other media used for in vitro of various gas production techniques were discussed by Rymer et al. (2005); different media may affect final pH and volume of CO2 produced per ml of acid.
Calibration of the pressure sensors. The 125‐ml Wheaton flasks were incubated without feed and rumen fluid to measure the response of the sensor to changes in the pressure inside the flasks. Ten ml of CO2 were injected into the sealed‐flasks and voltage was measured. This process was repeated 8 times in order to generate enough data points to plot voltage readings on gas volume added. Two sets of flasks (22 flasks/set) were calibrated. The volume of the flasks were determined by adding water at 25oC until full. The volume of the stir and the rubber were discounted from the final volume.
3
Calculation of the volume from voltage and adjustment of the gas production of the in vitro fermentation to the gas production of blank flasks. The raw voltage readings (V) are converted to gas volume (ml) using individual conversion ratios between voltage and volume obtained during the calibration of the pressure sensors. Usually, two blanks (i.e. flaks without feed) are used to adjust the gas production due to fermentation of nutrients contained in the rumen fluid. The voltage measured in the blanks are converted to gas volume and averaged for each time point. This blank volume average is subtracted from the volume of each flask for each time. Concomitantly, the gas volume was also normalized for the same amount of substrate, usually 100 g of DM, as shown in Equations [5] to [7].
( )0 , 100t t Blank tt
Adj
Voltage Voltage GasGas
Substrate=⎡ ⎤− ×Δ − ×⎣ ⎦= [5]
(,Blank t t tGas Voltage Voltage == − )0 ×Δ [6]
1000Adj AFSubstrate Substrate DM= × × [7]
Where Gas is the gas produced, ml; Voltage is measured by the pressure sensor, V; Δ is the change in ml per change in voltage (Equation [13]), ml/V; and DM is dry matter of the substrate, fractional.
The effect of adjustment for gas production was investigated. The exponential model with discrete lag (Equation [8]) was fitted to 19 gas production profiles of corn dry distillers’ grain (DDG) from 4 different types of DDG. The gas production profiles were either adjusted or not adjusted for the gas production of the mean of two blank flasks. The blank flasks contained media (phosphate‐bicarbonate buffer) and rumen fluid. The nls function (Bates and Chambers, 1993) of R 2.7.2 (R Development Core Team, 2008) was used to converge the data to Equation [8] using the “port” algorithm (Fox et al., 1978; Gay, 1990).
( )(1 ); 00; 0
b t ca e tVt
− × −⎧ × − ∀ ≥= ⎨
∀ <⎩ [8]
A random coefficients model (Littell et al., 2006) was fitted to the parameter’s estimates of Equation [8], including the sum of square of errors (SSE), to compare the impact of the adjustment on the estimates using the function lme (Pinheiro and Bates, 2000) of R (R Development Core Team, 2008). The following R code was used to generate the lme analysis, to check for the normality, identically distributed, and independency assumptions of the residuals, and to obtain the 95% confidence interval of the estimates in which type means adjusted or unadjusted values and ddg means the DDG type.
> # load library nlme > library(nlme) > # mixed model analysis > lme.a<‐lme(fixed=a~type, data=data1, random=~1|ddg) > summary(lme.a) > # perform ANOVA analysis and F‐test > anova(lme.a) > # plot observed x fitted, residuals x predicted, and normality plot > plot(lme.a,a~fitted(.))
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> plot(lme.a) > qqnorm(lme.a,~resid(.)|ddg) > # compute the 95% confidence intervals for random and fixed variables > intervals(lme.a)
Results and Discussion
Material and cost. Table 3 has the list of material and cost for building a fermentation chamber with 11 pressure sensors. The cost of the fermentation chamber was $ 4,235.84. This value does not include the material and labor involved in making the aluminum supporters for the pressure sensor and the stirrers ($ 300). Therefore, the fixed cost was $ 4,535.84 without labor. The cost for adding another ADC and additional 11 pressure sensors was about $ 1,044.04. The fixed cost for a 22‐pressure sensor would be about US$ 5,600. Additional fixed cost should be added such as IBM‐PC and accessories.
Calibration of the pressure sensors. The 125‐ml flask sets A and B had a linear response between voltage (V) and gas added to the flask (ml). The mean and SD of intercepts and slopes were 0.52 ± 0.02 V and 64.52 ± 3.74 ml/V, and 0.49 ± 0.02 V and 64.31 ± 2.2 ml/V; respectively. The volume of the flasks were 137.5 ± 1.16 and 137.9 ± 0.54 ml; respectively. These measurements were done on the same day. There is no clear evidence why the SD were different between these sets. Pell and Schofield (1993) have indicated a slope of 8.88 ml/V on 50‐ml Wheaton flasks. As discussed above, the relationship between voltage and pressure of the pressure sensor and ADC used is 0.32 V at 0 atm and 2.5 V at 1 atm. Therefore, Equation [9] was obtained to indicate this relationship.
Voltage,V 0.32 2.18 Pressure,atm= + × [9]
The ratio of the CO2 in the liquid phase to the CO2 in the gas phase is computed using Equation [10], using the Henry’s Law to compute pressure and volume relationship of CO2 (Pell and Schofield, 1993; Schofield and Pell, 1995) and assuming 20 ml of liquid (media plus rumen fluid) in the flask.
[ ][ ]
2
2
200.024620
Liquid
Gas
COR T
CO Flask Volume= × × ×
− [10]
Where R is the universal gas constant, 0.082 L∙atm/(mole∙K) and T is temperatue, oK.
If X ml of gas is added to a flask containing an aqueous solution, some of it will dissolve. Schofield and Pell (1995) derived Equation [11] to compute the fraction of remaining gas in the gas phase.
[ ][ ]
2
2
1
1 Liquid
Gas
fCO
CO
=
+
[11]
Thus, X ml of gas would produce a voltage change (ΔV) as indicated in Equation [12].
5
2.18Flask volume - 20
X fV × ×Δ = [12]
Rearranging Equation [12], one can compute the ml produced per change in voltage as shown in Equation [13] (Schofield and Pell, 1995).
Flask volume - 202.18
mlV f
=Δ ×
[13]
Hence, assuming a temperature of 39 oC (312 oK: oK = oC + 273) and the flask volumes for set A and B, the [CO2]Liquid/[CO2]Gas (Equation [10]) is 0.1072 and 0.1067 for sets A and B; respectively.
Therefore, f (Equation [11]) would be 0.9032 and 0.9036 for sets A and B; respectively, and the ml/ΔV (Equation [13]) would be 59.7 and 59.9 ml/V; respectively for sets A and B. These values are 8.2 and 7.6% below the measured values (64.5 and 64.3 ml/V; respectively). This difference is likely caused by a greater proportion of CO2 going into solution and differences among sensors. The individual measured
values are used to compute ml of gas produced per ΔV of each flask. Adjustments for methane can also
be made (Schofield and Pell, 1995); the calculated ml/ΔV values would be smaller than those without methane adjustment.
Figure 5 depicts the fermentation dynamics measured as voltage and volume for alfalfa hay and dry distillers’ grain. The pattern of fermentation was not similar within the same feed likely because the adjustment for the gas production of the blank flasks might have changed the pattern. This may not be a valid direct comparison of the effect of adjustment. It is common to utilized the gas production of blank flasks (i.e. flaks without feed but with media and rumen fluid) to correct for gas released from rumen fluid substrates, allowing for comparisons between incubations completed on different days or in different batches (Menke and Steingass, 1988). Table 4 shows a direct comparison of parameter estimates when fitting Equation [8] to the gas production measurement with and without adjustment for gas production of the average of two blank flasks. The unadjusted profiles had greater (P < 0.01) asymptote (estimate a), fractional rate of fermentation (estimate b), and SSE; but had lower (P < 0.01) lag time (estimate c) compared to adjusted profiles. Therefore, the pattern of fermentation is changed when adjusting for blank flasks fermentation. Carro et al. (2005) have reported similar impacts when adjusting gas production for blanks. These authors concluded that using blanks for correction purposes can change interpretation of results. Despite these findings, the authors suggested the inclusion of blanks to compare gas production. Similarly, Rymer et al. (2005) concluded the gas production of blanks should not be subtracted from the gas production of the sample being tested because the dynamics of the fermentation are different, including the rate of fermentation (Cone, 1998).
Future developments
Future developments should include more stable double‐function electrodes and measure pH at the same time pressure is being measured. In addition, a special electrode to concurrently measure ammonium and ammonia production could be used to determine protein fermentation at the same time.
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Acknowledgements We would like to express our appreciation to the students that have contributed in one way or another with experimental and laboratorial procedures of these projects. Special thanks for Dr. Judson Vasconcelos and Dr. Mario Chizzotti for helping with the design and construction the fermentation chamber.
Literature Cited
Bates, D. M. and J. M. Chambers. 1993. Nonlinear Models. Pages 421‐454 in Statistical Models in S. J. M. Chambers and T. J. Hastie, ed. Chapman & Hall, New York.
Carro, M. D., M. J. Ranilla, and M. L. Tejido. 2005. Using an in vitro gas production technique to examine feed additives: Effects of correcting values for different blanks. Animal Feed Science and Technology. 123‐124:173‐184.
Cherney, D. J., J. Siciliano‐Jones, and A. N. Pell. 1993. Technical note: forage in vitro dry matter digestibility as influenced by fiber source in the donor cow diet. J. Anim. Sci. 71(5):1335‐1338.
Cone, J. W. 1998. The development, use and application of the gas production technique at the DLO Institute for Animal Science and Health (ID‐DLO), Lelystad, The Netherlands. Pages 65‐78 in In vitro Techniques for Measuring Nutrient Supply to Ruminants. Occasional Publication No. 22, Penicuik, UK. British Society of Animal Science.
Cone, J. W., A. H. Van Gerder, G. J. W. Visscher, and L. Oudshoorn. 1996. Influence of rumen fluid and substrate concentration on fermentation kinetics measured with a fully automated time related gas production apparatus. Animal Feed Science and Technology. 61:113‐128.
Fox, P. A., A. P. Hall, and N. L. Schryer. 1978. The PORT mathematical subroutine library. ACM Transactions on Mathematical Software (TOMS). 4(2):104‐126.
Gay, D. M. 1990. Usage summary for selected optimization routines. Computing Science Technical Report. No. 153. AT&T Bell Laboratories, Murray Hill, NJ. 21 p. Available at: http://netlib.bell‐labs.com/cm/cs/cstr/153.pdf.
Goering, H. K. and P. J. Van Soest. 1970. Forage fiber analysis: Apparatus, reagents, procedures, and some applications. Agric. Handbook. No. 379. ARS, USDA, Washington, DC. 1‐20 p.
Huntington, J. A. and D. I. Givens. 1995. The in situ technique for studying the rumen degradation of feeds: A review of the procedure. Nutrition Abstracts and Reviews (Series B). 65(2):63‐93.
Littell, R. C., G. A. Milliken, W. W. Stroup, R. D. Wolfinger, and O. Schabenberger. 2006. SAS for Mixed Models (2nd ed.). SAS Institute, Cary, NC.
Menke, K. H. and H. Steingass. 1988. Estimation of the energetic feed value obtained from chemical analysis and in vitro gas production using rumen fluid. Animal Research and Development. 28:7‐55.
Nocek, J. E. 1988. In situ and other methods to estimate ruminal protein and energy digestibility: a review. J. Dairy. Sci. 71:2051‐2069.
Pell, A. N. and P. Schofield. 1993. Computerized monitoring of gas production to measure forage digestion in vitro. J. Dairy. Sci. 76:1063‐1073.
Pinheiro, J. C. and D. M. Bates. 2000. Mixed‐Effects Models in S and S‐Plus. Springer, New York. R Development Core Team. 2008. R: A language and environment for statistical computing. R
Foundation for Statistical Computing, Vienna, Austria. Rymer, C., J. A. Huntington, B. A. Williams, and D. I. Givens. 2005. In vitro cumulative gas production
techniques: History, methodological considerations and challenges. Animal Feed Science and Technology. 123‐124:9‐30.
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Sayre, K. D. and P. J. Van Soest. 1972. Comparison of Types of Fermentation Vessels for an In Vitro Artificial Rumen Procedure. J. Dairy. Sci. 55(10):1496‐1498.
Schaefer, D. M., C. L. Davis, and M. P. Bryant. 1980. Ammonia saturation constants for predominant species of rumen bacteria. J. Dairy. Sci. 63:1248‐1263.
Schofield, P. 1996. An inexpensive incubator for the biology laboratory. American Biology Teacher. 58:494‐498.
Schofield, P. and A. N. Pell. 1995. Validity of using accumulated gas pressure readings to measure forage digestion in vitro: A comparison involving three forage. J. Dairy. Sci. 78:2230‐2238.
Tilley, J. M. A. and R. A. Terry. 1963. A two‐stage technique for the in vitro digestion of forage crops. Journal of the British Grassland Society. 18:104‐111.
Vanzant, E. S., R. C. Cochran, and E. C. Titgemeyer. 1998. Standardization of in situ techniques for ruminant feedstuff evaluation. J. Anim. Sci. 76:2717‐2729.
Varel, V. H. and K. K. Kreikemeier. 1995. Technical note: Comparison of in vitro and in situ digestibility methods. J. Anim. Sci. 73:578‐582.
A B
CD
Figure 1. Pictures of the (A) computerized gas production boxes (blue and red) developed at Cornell University, Ithaca, NY, (B) detail of the inside of the blue box, (C) incubation undergoing in the red box , and (D) detail of the pressure sensor (see Pell and Schofield, (1993)).
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A
B
C
Figure 2. Elements used to build a fermentation chamber: (A) pressure sensor and connections, (B) analog‐to‐digital converter card from PicoTech, (C) built printed circuit board showing the details of the voltage dividers and the terminal board from PicoTech.
10
A B
C D
Figure 4. Picture of (A) the outside of the fermentation chamber and IBM‐PC, (B) the inside of the fermentation chamber, showing 250‐ml Wheaton flasks, pressure sensors, and cables with a capacity to ferment 22 samples, (C) support for 120‐ml Wheaton flaks, and (D) stirrer’s
rotors (four) with a switch (top right).
12
1 2
3
4
5
Figure 5. Fermentation dynamics of alfalfa and dry distillers’ grain measured as voltage (unadjusted for blank) and volume (adjusted for blank).
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
0
5
10
15
20
25
30
0 4 8 12 16 20 24 28 32 36 40 44 48
Voltage, V
Gas volum
e, m
l
Time, h
Alfalfa ‐ Adj DDG ‐ Adj. Alfalfa ‐ Unadj. DDG ‐ Unadj.
Unadjusted
Adjusted
13
6 7
Table 1. Macro and micro solutions for in vitro anaerobic fermentation of feeds proposed by Goering and Van Soest ((1970))
Formula Chemical Quantity Code Price (US$) Cost (US$/g)Macro solution Na2HPO4 Sodium phosphate dibasic 5.7 g S 374‐ 500g 74.02 (500g) 0.148 KH2PO4 Potassium phosphate monobasic 6.2 g P 284‐ 500g 44.72 (500g) 0.089 MgSO4.7H2O Magnesium sulphate heptabasic 0.6 g M 63‐ 500g 98.51 (500g) 0.197 Micro solution CaCl2.2H2O Calcium chloride 13.2 g C 79‐ 500g 71.47(500g) 0.143 MnCl2.4H2O Manganese chloride 10 g M 87‐ 100g 36.90 (100g) 0.369 CoCl2.6H2O Cobalt chloride 1.0 g C 371‐ 100g 79.98 (500g) 0.799 FeCl3.6H2O Ferric chloride 8.0 g I 88‐ 500g 104.43 (500g) 0.21
8
9
10
11
12
Average cost of the macro solution is US$ 1.51/l and the micro solution is US$ 80.50/l.
Table 2. Micro solution for in vitro anaerobic fermentation of feeds used by Schaefer et al. ((1980))
Formula Chemical Quantity Code Price (US$) Cost (US$/g)
Na4 EDTA Sodium EDTA 500 mg S 657‐ 500g 125.91(500g) 0.25FeSO4.7H2O Ferrous sulfate heptabasic 200 mg I 146‐ 500g 92.50 (500g) 0.185MnCl2.4H2O Manganese chloride 200 mg M 87‐100g 36.90 (100g) 0.369ZnSO4.7H2O Zinc sulfate heptabasic 10 mg Z 76‐ 500g 56.50 (500g) 0.113H3BO3 Boric acid 30 mg A 74‐ 500g 73.16 (500g) 0.146CoCl2.6H2O Cobalt chloride hexabasic 20 mg C 371‐ 100g 79.98 (100g) 0.8CuCl2.2H2O Cupric chloride 1 mg C 454‐ 500 g 112.02 (500g) 0.224NiCl2.6H2O Nickel chloride 2 mg N 53‐ 500g 78.45 (500g) 0.157NaMoO4.2H2O Sodium molybdate 3 mg S 336‐ 500g 342.50 (500g) 0.685
13
14
15
Average cost of the micro solution is US$ 0.26/l.
14
15
16 Table 3. Cost (US$) and material used to build the fermentation chamber with 11 pressure sensors
Description Cost Q TotalWood chamber 1 1/2'' dec choice 1.86 1 1.86 1/2 pt amer acct 3.48 1 3.48 1/2x4x8 blondewood 24.93 1 24.93 1/2x4x8 sheath r 10.38 1 10.38 12‐10awg 8‐10s te 1.88 1 1.88 12'x 1/2'' powerl 7.44 1 7.44 16oz titebond ori 3.98 1 3.98 1x2x4' select pin 1.98 1 1.98 1x2x4' select pin 1.98 3 5.94 1x3x4' select pin 3.30 1 3.30 2'' foam 0.57 2 1.14 2.8 oz silicone I 3.28 1 3.28 2‐1/2 sfty hasp z 2.30 1 2.30 3'' foam 0.74 1 0.74 3'' Trim Roller sh 1.98 1 1.98 3/4X20X48 stain g 18.03 1 18.03 3‐1/2 FM Hinges B 5.88 1 5.88 3‐1/2 hinges sb/p 8.88 3 26.64 4x1/2 ph fl wood 2.95 1 2.95 5 pk 9x11 Bare wood 2.17 1 2.17 5.2 mm type 1 ext 9.69 1 9.69 60ut.1000jsurge 12.46 1 12.46 60W DL clear 2pk 3.28 1 3.28 6‐1/2 pull zn 2.18 2 4.36 Assorted lighted 16.97 1 16.97 Bosch # 1 Phillips 2.78 1 2.78 Cleat receptacle 2.60 1 2.60 Cleat receptacle 2.60 1 2.60 Commercial grade 1.97 1 1.97 Drywall screw fin 4.47 1 4.47 Fan axial 30 cfm 115 v 22.24 2 44.48 Gang nm handy 0.63 2 1.26 Gear motor, 30 rpm 115 vac 41.42 4 165.68 Handy box duplex 0.44 2 0.88 Hole saw 2 1/4'' 4.97 1 4.97 Hole saw 2 3/4'' B 17.47 1 17.47 Instant change ut 9.88 1 9.88 Jh .85 Oz Quickse 2.97 1 2.97 Knob rd porcelain 1.68 1 1.68 Large hook 2.97 2 5.94 M‐P Foam tape 3/8 2.88 2 5.76 Qt. amer. Trad ext. 9.97 1 9.97 Resi receptable 2 0.44 2 0.88 Sp Black shield D 9.97 1 9.97 Thermostat/Temp. control 53.78 1 53.78 Toggle switch 3.96 1 3.96 Toggle, spst 3.82 1 3.82 TOTAL 534.81 CO2 set up Fitting ss 1/8'' 51.25 6 307.50 Tee 1/8" 316ss ea 19.00 4 76.00 Adapter 1/8"x1/8" 6.00 6 36.00 Fitting hose to male luer 23.00 5 115.00 Tubing viton 1/4x5/16" 25' 66.00 1 66.00 Ratchet tubing clamps 40.00 1 40.00 Needle blunt end 18gx6" 109.50 1 109.50 Fitting adapt.1/8"x1/4" 1/pk 23.00 6 138.00 TOTAL 888.00
Description Cost Q TotalChamber electronics
6' SHLD RS232 M‐F 13.99 1 13.99Hose clamp pincers‐standard 26.10 1 26.10Hose clamps s/s 2.45 1 2.45Hose clamps s/s (pack with 10) 19.55 2 39.10Male luer w/locking nut 3/32'' 4.25 3 12.75Mini voltage pressure sensors 60.00 1 60.00Mini voltage pressure sensors 40.00 15 600.00PVC tubing 3/32'' 2.65 1 2.65USB 11/12 with terminal board 287.00 1 287.00
TOTAL 1044.44 Other Electronics
AC power cable plug 15A 250V 2.68 2 5.36Antex soldering iron g/3u 20.48 1 20.48Antex solder iron tip#8‐1 4.38 1 4.38Box alum 7''x5''x3'' CU‐3008A 8.06 2 16.12Cable 3 conductor 22AWG shield 0.32 60 19.20Hi rel 8 pin socket 0.37 30 11.10Socket solder tail 8dip 208‐G49d 0.11 1 0.11Multimeter m‐3800 3 1/2 digital 49.97 1 49.97Nylon nut 6‐32 0.09 8 0.72Nylon screw 6‐32x3/4 0.09 8 0.72Phone plug min 3‐con 0.66 22 14.52Phone plug min 3‐con 0.60 2 1.20Phone plug min 3‐con 0.60 10 6.00Phone socket min 2‐cond open 0.49 2 0.98Phone min 3‐cond 33‐724 0.62 22 13.64Phone min 3‐cond 33‐724 0.62 11 6.82Protoboard JE‐25 wide for 25‐IC 22.44 1 22.44Protoboard copper‐clad perf bd 6.88 2 13.76Protoboard copper‐clad perf bd 6.88 1 6.88Resistor carb 1/4W 5% (10R‐2M) 0.04 30 1.20Resistor carb 1W 5% (.1R‐10M) 0.19 4 0.76Resistor carb 1W 5% (10R‐22M) 0.04 30 1.20Solder 63/37 .025" kester 10.29 1 10.29Solder iron holder 12.39 1 12.39Switch min toggle 1P on/on 1.5A 1.68 2 3.36Test lead set min clips 6.12 1 6.12Transformer 12vdc 500mA 3.5 6.38 2 12.76Trimpot 15turn 3/4'' 3006P‐1 1.42 4 5.68Trimpot single 200k 3386Y‐1 1.08 30 32.40Trimpot single 5k 3386Y‐1 1.06 30 31.80Washer nylon #6 0.04 8 0.32wire hookup 24AWG 1550 0.08 45 3.60Wire jumper kit 22AWG assorted 17.80 1 17.80Wire solid for wire wrap 0.11 2 0.22
TOTAL 354.30 Laboratory material
Al weighing dish (F08‐732‐101) 15.30 3 45.90Decrimpers 171.92 1 171.92Gloves ‐ Fisher 19‐048‐557D 268.92 1 268.92Hand crimpers (10‐319‐490) 171.66 1 171.66Lubriseal (stopcock grease) 19.66 1 19.66Magnetic stir bar (F14‐511‐60B) 66.90 1 66.90Needle (14‐826D) 7.93 2 15.86Stopper (06‐406‐11B) 98.32 1 98.32Stoppers ($0.37 x 600) 222.00 1 222.00Aluminum seal (06‐406‐14B) 48.55 1 48.55Wheaton 125 ml (06‐406K) 285.00 1 285.00
TOTAL 1414.69 OVERALL TOTAL 4235.84
Table 4. Comparison of parameter estimates of an exponential model with discrete lag to gas production measurement with and without adjustment for gas production of the blank flasks for four
types of corn dry distillers’ grain using random coefficients model
Item Adjusted Unadjusted SEM P-value AIC σDDG σ a, ml 21.5 29.1 1.75 < 0.001 137 3.45 1.11 b, %/h 9.86 10.8 0.56 0.0032 -213 0.01 0.0092 c, h 0.25 0.01 0.07 0.0001 -6.27 0.106 0.172 Fitting SSE, ml2 98.5 189 35.6 0.0001 422 65.1 63.1
16