A very high level of alkalophilic and thermostable pectinase and xylanase has been produced from newly isolated strains of Bacillus subtilis and Bacillus pumilus respectively. Enzyme production for pectinase was carried out under SSF using combinations of cheap agricultural residues while xylanase was produced under submerged fermentation using wheat bran as substrate to minimize the cost of production of these enzymes Among the various substrates tested, the highest yield of pectinase production was observed by using combination of WB + CW (6592 U/g of dry substrate) supplemented with 4% yeast extract when incubated at 37 °C for 72 h using deionized water of pH 7.0 as moistening agent. The biobleaching effect of these cellulase free enzymes on kraft pulp was determined. Both xylanase and pectinase showed stability over a broad range of pH from 6 to 10 and temperature from 55 to 70 °C. The bleaching efficiency of the pectinase and xylanase on kraft pulp was maximum after 150 min at 60 °C using enzyme dosage of 5 IU/ml of each enzyme at 10% pulp consistency with about 16% reduction in kappa number and 84% reduction in permanganate number. Enzyme treated pulp when subjected to CDED1D2 steps, 25% reduction in chlorine consumption and upto 19% reduction in consumption of chlorine dioxide was observed for obtaining the same %ISO brightness. Also an increase of 22 and 84% in whiteness and fluorescence respectively and a decrease of approximately 19% in the yellowness of the biotreated pulp were observed by pretreatment of the pulp with our enzymatic mixture.
5 December 2007 in Applied Biochemistry and Biotechnology
Two contrasting cyanobacterial species ( Anabaena fertilissima and Anabaena sphaerica ) were selected based on differences in antifungal behavior in order to study the mechanism for production of an antifungal enzyme and the genes responsible for this production. In A. fertilissima , chitosanase and antifungal activities were increased significantly under of growth-limiting conditions (8 of light and 16 h of darkness). The lack of such activities in A. sphaerica was associated with high levels of protein that accumulated during the stationary phase (at 28 days) under the same light conditions. The gene putatively responsible for chitosanase and antifungal activities was amplified using specific primers, and sequence analysis of the amplified products (1.086 and 1.101 kb in A. sphaerica and A. fertilissima , respectively) showed that they belong to the glycoside hydrolase 3 (GH3)-like family of Anabaena variabilis ATCC 29413. Pairwise alignment of the corresponding protein sequences identified a putative signal peptide (amino acids 1 to 23) and some amino acid changes in the sequence of A. fertilissima which may be responsible for functioning of the chitosanase and the observed antifungal activity. Hydrolysis of the chitosan oligosaccharide (GlcN) 5 to (GlcN) 2 and (GlcN) 3 confirmed the presence of chitosanase activity in A. fertilissima . Site-directed mutagenesis of the A. fertilissima chitosanase-encoding gene ( cho ) led to identification of catalytic residues (Glu-121 and Glu-141) important for the antifungal effect of the cho product. The level of expression of cho was monitored by quantitative real-time reverse transcription-PCR, which indicated that transcription of this gene is significantly enhanced under conditions that retard growth, such as a long dark period.
The development of bioink-based 3D-printed scaffolds has revolutionized bone tissue engineering (BTE) by enabling patient-specific and biomimetic constructs for bone regeneration.