Silage juice

A CC chromatogram of a mixture of known VFAs, lactic acid and pivalic acid (internal standard) is shown in Fig. 8.3, and a chromatogram of a silage juice extract with pivalic acid internal standard is shown in Fig. 8.4. 

Fig. 8.3. GC chromatogram of mixed silage juice standards using a Carbopack B-DA column. Identity and concentrations (before diluting 4 1 standard 0.3 M oxalic acid) a, ethanol, 1 mg mM b, acetic acid, 1.25 mg mM c, propionic acid, 0.25 mg ml" d, isobutyric acid, 0.25 mg mM e, n-butyric acid, 0.25 mg mM f, pivalic acid (internal standard), 0.4 mg mM g, isovaleric acid, 0.25 mg mM h, lactic acid, 10 mg mM i, n-valeric acid, 0.25 mg mM j, isocaproic acid, 0.25 mg mM k, n-caproic acid, 0.25 mg mM.

Fig. 8.4. GC chromatogram of a third-cut silage juice using a Carbopack B-DA column. Identity a, ethanol b, acetic acid c, propionic acid e, n-butyric acid f, pivalic acid (internal standard), 0.32 mg mM in injected solution h, lactic acid.

The peak at 17.34 min is 50 pg ml mesaconic acid which was added as a possible internal standard, but it proved unsuitable because of an unknown peak eluting at 16.78 minutes seen when analysing silage juice without added internal standard oxalic acid suffered from the same problem. We still need a suitable internal standard for this column, thus further use was suspended. Other failed compounds included adipic acid, fumaric acid, D-glucuronic acid, glutaric acid, glycolic acid, 3-hydroxybutanone, itaconic acid, malic acid, maleic acid, malonic acid, pimelic acid and succinic acid. 

Extractor - the extractor is shown in Fig. 8.7, and the means of attaching the small torque wrench in Fig. 8.8. Ideally it should be constructed from stainless steel, but we only used a stainless steel threaded rod or studding (10 X % in, 11 t.p.i., or 254 x 15.9 mm), and the rest was machined from brass. The silage juice should not remain in contact with the brass for long, however, because the brass will be attacked by the acids. The dimensions... 

Fig. 8.8. Attachment of torque wrenoh to silage juice extractor by means of a socket.

Jones, D.W. and Kay, J.J. (1976) Determination of volatile fatty acids C. -Cg, and lactic acid in silage juice. Journal of the Science of Food and Agriculture 27, 1005-1014. 

A standard official method has been issued for the determination of Ci to C6 volatile carboxylic acids and lactic acid in silage juice [5,6]. 

Ministry of Agriculture, Fisheries and Food (1973) The Analysis of Agricultural Materials - Volatile Fatty Acids (Ct -Cl6) and Lactic Acid in Silage Juices, Method 85, Technical Bulletin RB 427, HMSO, London, UK. 

Thang, V.H. and S. Novalin, Green Biorefinery Separation of Lactic Acid from Grass Silage Juice by Chromatography using Neutral Polymeric Resin, Bioresource Technol., Corrected Proof (2007). 

Instead of expensive complex nitrogen sources cheaper products like silage juice [49] or meat and bone meal hydrolysate can successfully be applied in PHA production processes [39]. 

Matrices covered in this section are very diverse. Examples listed in Table 13.3 include silage juice, fermentation products, hydrolysated biomass residue, cellulose polymer, and also biological specimens. Although these matrices do not strictly classify as environmental samples, some analytical methods dealing with these matrices were included to show their unique approach. Motivations for the analyses are as diverse as the matrices themselves. 

Other matrices analyzed for organic acids include landfill leachates and samples derived from biological material such as silage juice, root exudates, or fermentation products. 

Ulber, R., Schneider, K., Peifer, S., and Heinzle, E. (2013) Production of L-lysine on different silage juices using genetically engineered Corynebacterium glutamicum. J. BiotechnoL, 163 (2), 217-224. 

Thang VH, Novalin S. Green biorefinery separation of lactic acid from grass silage juice by chromatography using neutral polymeric resin. Bioresour Technol 2008 99 4368-79. 

Madrid, J., A. Martinez-Teruel, F. Hernandez, and M. D. Megias. 1999. A comparative study on the determination of lactic acid in silage juice by colorimetric high-performance liquid chromatography and enzymatic methods. J. Sci. Food Agric. 

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