جستجوی مقالات مرتبط با کلیدواژه « xylan » در نشریات گروه « کشاورزی »

Antifungal compounds of Trichoderma spp, including various lithic enzymes, have a important role in biological control of pathogenic agents. Xylan is a group of hemicellulose compounds which are present in the cell wall of plants and some algae. Green algae and green-blue algae having pectin, cellulose, xylan hemicellulose, arabinoxylan, etc., in their structures could be considered as suitable inducer and precursor of cellulase, xylanase, and pectinase enzymes production in fungi. Beta-xylanase genes, including Xyn1 and Xyn2 genes in Trichoderma species cause to produce the Glycoside hydrolase family 10, enzyme. In this study, the effect of aqueous extract of green microalgae Scenedesmus obliquus on enzyme production ability of four Trichoderma species was investigated. For this purpose, aqueous algae extract at concentrations of 500 and 1000 µg/ml were used during 4 and 8 days to enzyme production was investigated. Change in expression level of Xyln-related gene was analysied using real-timePCR method. The results of this study showed a positive and variable effect of algae extract in enzyme production in all the treated Trichoderma species. The maximum amount of enzyme secretion was observed at concentration of  1000 µg/ml during 8 days of treatment in T. reesei species. At this concentration and time period, T. atroviride showed the lowest amount of enzyme production. Gene expression analysis showed that, the maximum level of Xylan gene expression was occured in T. reesei species at concentration of 1000 µg/ml during 8 days of treatment. Based on these results, it can be concluded that the compounds in cellulosic structure of Scenedesmus mico-algae can have a considerable effect on enzyme secretion of fungi and then can be used as an enzyme stimulus in fungi in industrial and large -scale projects.

Bio-refinery includes technologies which can convert biomass resources to valuable products. In this study, carboxymethylation of the xylan-rich hemicelluloses extracted from sugarcane bagasse pith was performed. DS of the carboxymethyl xylan (CMX) was determined 0.68 using ICP-OES analysis. The presence of absorption bands at 1580 and 1311 cm-1 in the FTIR spectrum of the modified xylan are associated to the stretching vibration of C-O bonds of carboxymethyl groups. The carboxymethyl xylan/chitosan (CMX/CS) films were then prepared by casting method. XRD pattern showed that the intensity of the characteristic peaks of the chitosan reduced after film preparation which may be due to decreasing the crystalline nature of the film. SEM images showed that the surface of the film is uniform. The observed exothermic peak in DSC thermograms showed that the films degraded at higher than 200oC. Water vapor permeability (WVP) of the carboxymethyl xylan/chitosan film was measured 0.84± 0.1 g mm/m2 h kPa. Colorimetric analysis proved that the white index (WI) of the CMX/CS film increased as compared with xylan/chitosan film. In contrary, the yellow index (YI) of the CMX/CS film decreased. Swelling ratios of the CMX/CS and xylan/CS films were measured as 130.42 and 95.71 respectively. The prepared CMX/CS films exhibited higher tensile strength in compared to xylan/chitosan film. This may be resulted from the interactions between amine groups of chitosan and carboxyl groups of CMX. CMX/CS film exhibited the higher antibacterial activity against E. coli that S. aureus.

In order to Xylan extraction, bagasse pith, after alkaline pre-treatment and sodium chlorite bleaching, treated with different dosage of soda and then calculated extraction percentage and characterized with FT-IR. Produced xylan changed to xylose with diluted acid hydrolysis and after treatment with active carbon and ultrasonic, reduced sugar measured by HPLC. Then, obtained xylose was added to yeasts media of kluyveromyces marxianus and pichia stipites to evaluate its effects on their growth kinetic. Results showed that by increasing in soda dosage, xylan extraction percentage increased. Also, hydrolysis process alone can produced much sugar without active carbon and ultrasonic. Evaluation of yeasts growth kinetic showed that the speed of yeast growth in media including xylose was more than glucose one and so efficiency of these yeasts is much for C5 sugar as it can be used them for bio-products manufacture.