Extra Nitrogen Source Research Articles

Effects of carbon and nitrogen sources on the induction and repression of chitinase enzyme fromMetarhizium anisopliae isolates

Metarhizium anisopliae, an entomopathogenic hyphomycete, is being used effectively in Integrated Pest Management (IPM) system. Foliar application of these fungi is quite satisfactory as it invades its host by adhering to insect cuticles and formation of penetration structures called appresoria, which produces various extracellular enzymes, including chitinase that causes the insect cuticle breaching. The induction and repression mechanism of chitinase activity is not entirely understood and activity of this enzyme is different in response to different carbon and nitrogen sources. This report illustrates the effect of two carbon sources viz. colloidal chitin and dextrose and a nitrogen source, yeast extract on the chitinase production of fourteenM. Anisopliae isolates. The chitinase activity varied among the isolates and the different media used. A high enzymatic activity was observed in the medium containing an extra nitrogen source (yeast extract) followed by the medium containing colloidal chitin as a sole source of carbon and nitrogen. The exochitinase activity and the chitinase activity gel were also studied for the isolates showing high chitinase enzyme production. An array of chitinase isozymes were observed on chitinase activity gel with a common 14.3 kDa enzyme for all the isolates.

Degradation of quinoline by Rhodococcus sp. QL2 isolated from activated sludge

A novel aerobic gram-positive bacterial strain capable of utilizing quinoline as sole source of carbon, nitrogen and energy was isolated from activated sludge of a coke plant wastewater treatment process. The isolate was identified as Rhodococcus sp. QL2 based on its morphology, physiochemical properties in addition to the results from 16S rDNA sequence analysis. The optimum temperature and the pH for its growth were 35–40 °C and 8.0, respectively. Extra nitrogen sources stimulated the bacterial growth on quinoline. Strain QL2 had strong quinoline degradability, and its degradation kinetics could be described with Haldane's model. Strain QL2 also had a broad range of substrate utilization. Identification of intermediates by GC/MS showed Rhodococcus sp. QL2 degraded quinoline via two pathways simultaneously.

Ethanol production from maize silage as lignocellulosic biomass in anaerobically digested and wet-oxidized manure

In this communication, pretreatment of the anaerobically digested (AD) manure and the application of the pretreated AD manure as liquid medium for the simultaneous saccharification and fermentation (SSF) were described. Furthermore, fermentation of pretreated maize silage and wheat straw was investigated using 2 l bioreactors. Wet oxidation performed for 20 min at 121 °C was found as the most suitable pretreatment conditions for AD manure. High ammonia concentration and significant amount of macro- and micro-nutrients in the AD manure had a positive influence on the ethanol fermentation. No extra nitrogen source was needed in the fermentation broth. It was shown that the AD manure could successfully substitute process water in SSF of pretreated lignocellulosic fibres. Theoretical ethanol yields of 82% were achieved, giving 30.8 kg ethanol per 100 kg dry mass of maize silage.

Ammonium Hydroxide Detoxification of Spruce Acid Hydrolysates

When dilute-acid hydrolysates from spruce are fermented to produce ethanol, detoxification is required to make the hydrolysates fermentable at reasonable rates. Treatment with alkali, usually by overliming, is one of the most efficient approaches. Several nutrients, such as ammonium and phosphate, are added to the hydrolysates prior to fermentation. We investigated the use of NH4OH for simultaneous detoxification and addition of nitrogen source. Treatment with NH4OH compared favorably with Ca(OH)2, Mg(OH)2, Ba(OH)2, and NaOH to improve fermentability using Saccharomyces cerevisiae. Analysis of monosaccharides, furan aldehydes, phenols, and aliphatic acids was performed after the different treatments. The NH4OH treatments, performed at pH 10.0, resulted in a substantial decrease in the concentrations of furfural and hydroxymethylfurfural. Under the conditions studied, NH4OH treatments gave better results than Ca(OH)2 treatments. The addition of an extra nitrogen source in the form of NH4Cl at pH 5.5 did not result in any improvement in fermentability that was comparable to NH4OH treatments at alkaline conditions. The addition of CaCl2 or NH4Cl at pH 5.5 after treatment with NH4OH or Ca(OH)2 resulted in poorer fermentability, and the negative effects were attributed to salt stress. The results strongly suggest that the highly positive effects of NH4OH treatments are owing to chemical conversions rather than stimulation of the yeast cells by ammonium ions during the fermentation.

The effect of diluent gas and rapid thermal annealing on the properties of plasma-deposited silicon nitride films

The effects of diluent gases on the deposition rate, content of hydrogen bonds, etch rate, refractive index and fixed charge density of plasma-enhanced chemical vapour deposition silicon nitride films have been studied for various gas compositions. Post-rapid thermal annealing (RTA) of as-grown films was also performed in the temperature range 500–1100°C. From the results of optical emission spectroscopy it is suggested that metastable N2 molecules can contribute to silicon nitride film formation as an extra nitrogen source. Metastable N2 molecules may enhance the dissociation of other feed gases. Lower refractive index, higher deposition rate and higher NH bond density were obtained for silicon nitride films grown in N2 diluent as compared with films grown in H2 diluent. As the RTA temperature was increased, the content of hydrogen bonds was reduced and the film density increased. Hence the etch rate of silicon nitride films in buffered HF solution decreased with increasing RTA temperature. A minimum value of fixed charge density was obtained at the RTA temperature of 900°C for all the films investigated.