Compostability of Co-Extruded Starch/Poly(Lactic Acid) Polymeric Material Degradation in an Activated Inert Solid Medium

The aim of this work was to estimate the biodegradation of a co-extruded starch/poly(lactic acid) polymeric material using a vermiculite based inert solid medium which could simulate compost medium and enable us to achieve complete carbon balances. At the end of the test the mineralisation rate was compared to those obtained for co-extruded starch/poly(lactic acid) polymeric material degradation in compost. It was shown that the mineralisation rate after 45 days of degradation was similar in activated vermiculite medium to the one in compost. A protocol for both extraction and quantification of the carbon included in the different degradation by-products was proposed and the carbon balance of the polymer degradation was followed during the test with a satisfactory accuracy. As the non-degraded PLA and starch material had been retrieved during the test, the evolution of the glass transition temperature and the molecular weight of PLA could be followed. A two-step degradation mechanism was highlighted in inert solid medium, showing the fundamental role of abiotic reactions for PLA degradation in compost

Production and characterization of cellulolytic activities produced by Trichoderma longibrachiatum (GHL)

The indigenous cellulolytic fungus Trichoderma longibrachiatum (GHL) isolated from soil near an Algerian hot spring was used for the production of cellulases by submerged fermentation on Mandels medium with cellulose Avicel (1%) as the sole carbon source. Endoglucanase and filter paper activities of the wild-type strain of Trichoderma were compared to the hypercellulolytic mutated Trichoderma reesei Rut C-30, in shake flask cultures at 35°C. After seven days of fermentation, T. longibrachiatum show equivalent activities than T. reesei (10.61 IU/ml of endoglucanase (CMCase) and 2.04 IU/ml of filter paper activity (FPA)). On the other hand, the ß-glucosidase activity of Trichoderma GHL was twice more important than that of T. reseei. The influence of inoculum size on cellulase activities did not prove significant differences in enzymatic activities for spore concentrations between 105 and 108 spores/ml. The cellulases produced by the isolated strain were also characterized. The optimum temperatures were 55 and 60°C for endoglucanase and FPA, respectively. The endoglucanase was thermostable at 70°C after 5 h incubation, and it preserved 80% of the original activity. The half-life of the FPA appeared to be 3 h at 60°C. The endoglucanase was optimally active at pH 4.0, and the FPA was optimal at pH 4.0 and 5.0. These activities were stable at 50°C after 5 h incubation in a pH range of 3.0 to 6.0 and 4.0 to 6.0, respectively. These results suggest that the non-mutated strain T. longibrachiatum (GHL) should be an attractive producer for cellulases production.Keywords: Cellulase, Trichoderma reesei, Trichoderma longibrachiatum, submerged fermentation, characterizationAfrican Journal of Biotechnology Vol. 12(5), pp. 465-47

Optimization and partial characterization of endoglucanase produced by Streptomyces SP B-PNG23

Streptomyces sp. B-PNG23 was selected as a promising cellulolytic strain and tested for its ability to produce cellulases from agroindustrial residues. A pH value of 7 and temperature of 28 C were found to be optimal for maximum enzyme production. The highest endoglucanase activity was obtained in a medium comprised of wheat bran (2 g/l), yeast extract (2 g/l), NaCl (2 g/l), NH4Cl (2.5 g/l), and (0.4 g/l) of MgSO4. The enzyme was active at a broad range of pH (5-8) and temperatures (40-70 degrees C). The optimum pH and temperature were 6 and 50 degrees C, respectively. In the presence of metal ions Mn2+, Cu2+ and NH4+ the activity of the enzyme increased significantly. The enzyme retained 50% of its activity after heating at 50 degrees C for 6 h. This enzyme could be considered as a thermotolerant biocatalyst that could be utilized in biotechnological applications

Optimization and partial characterization of endoglucanase produced by Streptomyces sp. B-PNG23

Streptomyces sp. B-PNG23 was selected as a promising cellulolytic strain and tested for its ability to produce cellulases from agroindustrial residues. A pH value of 7 and temperature of 28°C were found to be optimal for maximum enzyme production. The highest endoglucanase activity was obtained in a medium comprised of wheat bran (2 g/l), yeast extract (2 g/l), NaCl (2 g/l), NH4Cl (2.5 g/l), and (0.4 g/l) of MgSO4. The enzyme was active at a broad range of pH (5-8) and temperatures (40-70°C). The optimum pH and temperature were 6 and 50°C, respectively. In the presence of metal ions Mn2+, Cu2+ and NH4 + the activity of the enzyme increased significantly. The enzyme retained 50% of its activity after heating at 50°C for 6 h. This enzyme could be considered as a thermotolerant biocatalyst that could be utilized in biotechnological applications

Different Pla Grafting Techniques on Chitosan

PLA grafting on chitosan has been successfully prepared with two different methods: a direct grafting method and the ROP method. The thermal properties showed that the copolymerization of PLA on the chitosan's chain by direct grafting is more thermostable than the one obtained by the ROP method