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.
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.
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.
SUMMARYRecovery of a bacterial alkaline proteinase after treatment of the fermentation broth with 16 different flocculating additives has been investigated. The polyelectrolyte Sedipur TF 5 was the most effective at 150 ppm and pH 7.0-9.0, giving a 74% yield of enzyme activity.
Aim Benzaldehyde occurs in a number of plants, especially in the family Rosaceae and in particular in the genus Prunus. In nature, there are more than 100 genera and 3,000 species in the Rosaceae family. The objective of this study was to investigate the chemical composition of leaf essential oil of peach (Prunus persica L.) and cherry laurel (Prunus laurocerasus L.) as a new potential source of natural benzaldehyde. Methods The essential oil was prepared by hydrodistillation, and chemical constituents were determined by GC-FID, GC-MS and chromatographic profiles were compared with each other. Results The results show that essential oil obtained from peach and cherry laurel leaves appear to be a promising source of natural benzaldehyde. Under laboratory conditions the benzaldehyde content in peach and cherry laurel leaves reached 95.5% and 99.7%, respectively. Conclusions Laboratory and pilot experiments confirmed that by processing of 200–300 kg of green leaves of various species of the genus Prunus, especially peach and cherry laurel, 1 kg of benzaldehyde can be obtained.
The aim of this study was to develop immobilized enzyme systems that reduce carbonyl compounds to their corresponding alcohols. The demand for natural aromas and food additives has been constantly growing in recent years. However, it can no longer be met by extraction and isolation from natural materials. One way to increase the availability of natural aromas is to prepare them by the enzymatic transformation of suitable precursors. Recombinant enzymes are currently being used for this purpose. We investigated trans-2-hexenal bioreduction by recombinant Saccharomyces cerevisiae alcohol dehydrogenase (ScADH1) with simultaneous NADH regeneration by recombinant Candida boidinii formate dehydrogenase (FDH). In a laboratory bioreactor with two immobilized enzymes, 88% of the trans-2-hexenal was transformed to trans-2-hexenol. The initial substrate concentration was 3.7 mM. The aldehyde destabilized ScADH1 by eluting Zn2+ ions from the enzyme. A fed-batch operation was used and the trans-2-hexenal concentration was maintained at a low level to limit the negative effect of Zn2+ ion elution from the immobilized ScADH1. Another immobilized two-enzyme system was used to reduce acetophenone to (S)-1-phenylethanol. To this end, the recombinant alcohol dehydrogenase (RrADH) from Rhodococcus ruber was used. This biocatalytic system converted 61% of the acetophenone to (S)-1-phenylethanol. The initial substrate concentration was 8.3 mM. All enzymes were immobilized by poly-His tag to Ni2+, which formed strong but reversible bonds that enabled carrier reuse after the loss of enzyme activity.
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