Energy variety of amaranth (Amaranthus spp.) was grown in large-scale trials in order to verify the capability of its cultivation and use as a renewable energy source in a biogas plant. The possibility of biogas production using anaerobic co-fermentation of manure and amaranth silage was verified in the experimental horizontal fermentor of 5 m3 volume, working at mesophilic conditions of 38-40 °C. The goal of the work was also to identify the optimum conditions for growth, harvesting and preservation of amaranth biomass, to optimize biogas production process, and to test the residual slurry from digestion process as a high quality organic fertilizer. The average yield of green amaranth biomass was 51.66 t.ha-1 with dry matter content of 37%. Based on the reached results it can be concluded that amaranth silage, solely or together with another organic materials of agricultural origin, is a suitable raw material for biogas production.
In order to optimize the thermophilic lactic acid fermentation on saccharose as the sole carbon source and improve the effectiveness of the process, alternative nitrogen sources were tested and a minimal broth composition was found. Of the alternative nitrogen sources, whey protein hydrolyzate (WPH) was the best; the broth composition was reduced from seven down to three items. Application of ammonium as a neutralizingagent instead of sodium hydroxide brought an important positivechange.
Reactions have been studied of l-(5-nitro-2-furyl)-2-nitroethylene with -NH, and -OH groups of low-molecular compounds (butylamine, aniline, glycine, taurine, glucosamine, tyramine, tryptamine, noradrenaline, histamine, ethanol, methanol, OH- ions) as well as biopolymers (ribonuclease, albumin DNA, RNA, Newcastle disease virus). With the low-molecular amines and alcohols it has been found that the reactions proceed as nucleophilic additions in aqueous medium, and the respective nucleophilic groups attack the more electrophilic C(1) atom of the exocyclic double bond of nitrofurylethylene. The modifications proved with the above-mentioned biopolymers in vitro indicate a possibility of direct interaction (without metabolic activation) between 5-nitro-2-furylethylenes and proteins or nucleic acids in vivo. These findings are significant from the point of view of recognizing mutagenic effect of nitrofurylethylenes and general biotoxicity of these compounds.
The recovery of bacterial extracellular alkaline and neutral proteinases was investigated using mineral hydrocolloid bentonite in combination with the organic flocculant Hernostan B for the removal of solid compounds and cells from fermentation broth. The flocculation was effective in the pH range of 7.0 -8.5at concentrations of bentonite of 2.0-5.0 g . dm-3 and Hernostan B of 1.0-5.0 g . d~n -~. The results show that, by means of this technique, it is possible to achieve a yield of proteinases above 90% on a laboratory, and up to 85% on a pilot plant scale.
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