BackgroundSolid bio-wastes (or organic residues) are worldwide produced in high amount and increasingly considered bioenergy containers rather than waste products. A complete bioprocess from recalcitrant solid wastes to methane (SW2M) via anaerobic digestion (AD) is believed to be a sustainable way to utilize solid bio-wastes. However, the complex and recalcitrance of these organic solids make the hydrolysis process inefficient and thus a rate-limiting step to many AD technologies. Effort has been made to enhance the hydrolysis efficiency, but a comprehensive assessment over a complete flow scheme of SW2M is rare.ResultsIn this study, it comes to reality of a complete scheme for SW2M. A novel process to efficiently convert organic residues into methane is proposed, which proved to be more favorable compared to conventional methods. Brewers’ spent grain (BSG) and pig manure (PM) were used to test the feasibility and efficiency. BSG and PM were enzymatically pre-hydrolyzed and solubilized, after which the hydrolysates were anaerobically digested using different bioreactor designs, including expanded granular sludge bed (EGSB), continuously stirred tank reactor (CSTR), and sequencing batch reactor (SBR). High organic loading rates (OLRs), reaching 19 and 21 kgCOD · m−3 · day−1 were achieved for the EGSBs, fed with BSG and PM, respectively, which were five to seven times higher than those obtained with direct digestion of the raw materials via CSTR or SBR. About 56% and 45% organic proportion of the BSG and PM can be eventually converted to methane.ConclusionsThis study proves that complex organic solids, such as cellulose, hemicellulose, proteins, and lipids can be efficiently hydrolyzed, yielding easy biodegradable/bio-convertible influents for the subsequent anaerobic digestion step. Although the economical advantage might not be clear, the current approach represents an efficient way for industrial-scale treatment of organic residues with a small footprint and fast conversion of AD.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0237-8) contains supplementary material, which is available to authorized users.
Ramirez-Ramirez, H. A., Geis, A. R., Heine, C. S., Clark, K. J., Gehman, A. M. and Kononoff, P. J. 2011. Storage conditions of wet corn distillers’ grains with solubles in combination with other feeds and understanding the effects on performance of lactating dairy cows. Can. J. Anim. Sci. 91: 331–339. Wet distillers’ grains are commonly stored in polyethylene silo bags until needed for feeding. The objective of the first experiment was to evaluate the nature of ensiling wet distillers’ grains with soluble (WDGS) alone or in combination with other feeds. A 3×4×3 factorial experiment was conducted in which 36 mixtures were made using three loads of distillers’ grains stored at varying levels with three feeds (corn silage, ground corn, and brome hay). In all mixtures, the addition of feeds to WDGS increased the pH of stored material. The objective of the second experiment was to evaluate the effects of feeding WDGS on milk production. Twenty Holstein cows were used in a 4×5 Youden square. Prior to initiation of the study, WDGS were stored alone (WDGS) or mixed with either 12% ground corn (DM basis) (WDGS+C), 15% brome hay (DM basis) (WDGS+H) or 15% corn silage (DM basis) (WDGS+CS) in polyethylene silo bags. Animals were assigned to one of five treatments during each 21-d period. A diet not containing WDGS was formulated (Control), along with one containing 30% WDGS (DM basis) (WDGS). Three additional diets, similar to the WDGS treatment, were formulated to include one of the three blends of WDGS with corn (WDGS+C), brome hay (WDGS+H) or corn silage (WDGS+CS). Dry matter intake (DMI) was affected by diet and, compared with Control (21.9 kg d−1±0.70 kg d−1), was greater for WDGS (23.8±0.70 kg d−1) and WDGS+C (23.7±0.70 kg d−1). Milk yield, 3.5% FCM, and fat yield were not affected by treatment. These results suggest that dairy rations can be formulated to include stored WDGS at 30% DM without negative effects on milk production and composition.
The fortification of animal feed with enzymes in order to optimize feed utilization has become a standard for the meat production industry. A method for measuring levels of active enzymes that can be carried out quickly would ensure that feed has been supplemented with the appropriate amount of enzyme. Phytase is the most widely used feed enzyme and is routinely quantified with an activity assay in a limited number of specialized laboratories. As an alternative, we report here the development of a rapid and easy method to perform a quantitative assay for the phytase from Citrobacter braakii. The method is suitable for use at local sites with a minimum lab setup and will reduce delays and potential interferences due to improper sample storage and shipment. The new assay is based on a lateral flow immunoassay that utilizes magnetic immune-chromatographic test (MICT) technology to quantify the phytase content of a feed extract. After extraction of the phytase from the feed, the sample is simply diluted and added to a reaction tube containing a specific anti-phytase antibody coupled to superparamagnetic particles. The mixture is then applied on an assay cassette, where the formed particle–antibody–phytase complexes are captured by immobilized antibodies on a nitro-cellulose strip housed in a cassette. The cassette is placed in the MICT reader that measures the magnetic signal of the captured particles. Using the calibration information stored in the cassette barcode, the signal is converted to a phytase concentration, given as phytase activity (FYT) per kilogram of feed. The accuracy and robustness of the assay compared to the ISO phytase activity assay were demonstrated through a large validation study including real feed samples from different compositions and origins. The MICT assay is the first quantitative assay for feed enzymes that is fast, reliable, and simple to use outside of a specialized reference laboratory and that is suitable for use in place of the current ISO assay.
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