Re-parameterization of the asymmetric model for fungal spore germination.

The asymmetric model (Dantigny et al., 2011, A new model for germination of fungi, International Journal of Food Microbiology, 146, 176-181) is capable to fit both symmetric and asymmetric curves of fungal spore germination. However, the shape parameter in the asymmetric model must be derived from a regression of the model with experimental data of fungal spore germination, thus the asymmetric model can fit spore germination under tested conditions only. In this paper, to solve this limitation, the previously proposed shape parameter-based asymmetric model has been replaced by using the pure biological parameter-based asymmetric model as: [Formula: see text] , where P is the percentage of germinated spores at time t, Pmax is the maximum percentage of germinated spores, τ is the germination time (the time that P = 0.5Pmax), and µ is the slope of fungal spore germination at t = τ, representing the rate of fungal spore germination. The modified asymmetric model was validated against the germination data of six fungal species collected from the literature. The results showed that the modified asymmetric model described the spore germination of all fungi studied well. Moreover, the τ and µ in the modified asymmetric model at various environmental conditions were estimated properly via the Cardinal Model with Inflection. This solved the limitation of the previous asymmetric model. So, it can be concluded that the modified asymmetric model is an improvement over the previous asymmetric model for predicting fungal spore germination.

Study of kinetic model for fungal spore germination under dynamic conditions: Case study on germination of Penicillium expansum spores.

The germination of fungal spores under non-isothermal conditions has been studied for several years, however, no mathematical model has been able to describe them suitably. Therefore, in this paper, we developed a new model to clarify the understanding of fungal spore germination under non-isothermal conditions by considering the effects of magnitude of condition change and difference in phase of spore during condition change on kinetic parameters, i.e., the mean rate of germination (µ) and the time that half of spores had germinated (th). To combine both effects into our new model, it was necessary to develop other two new models. The first model was used for estimating the swelling time of spores. The second model was the relationship between thvs µ. After we had completed both models and successfully combined both effects into the new model for fungal spore germination under non-isothermal conditions, the new model was validated against experimental data on germination of Penicillium expansum spores in the literature. The prediction results showed that the new model well described the germination of this fungus under non-isothermal conditions.

Study of Lignin Extracted from Rubberwood Using Microwave Assisted Technology for Fuel Additive.

Lignin is the most abundant natural aromatic polymer, especially in plant biomass. Lignin-derived phenolic compounds can be processed into high-value liquid fuel. This study aimed to determine the yield of lignin by the microwave-assisted solvent extraction method and to characterize some essential properties of the extracted lignin. Rubberwood sawdust (Hevea brasiliensis) was extracted for lignin with an organic-based solvent, either ethanol or isopropanol, in a microwave oven operating at 2450 MHz. Two levels of power of microwave, 100 W and 200 W, were tested as well as five extraction times (5, 10, 15, 20, 25, and 30 min). The extracted lignin was characterized by Klason lignin, Fourier transform infrared spectroscopy (FT-IR), 2D HSQC NMR, Ultraviolet-visible spectrophotometry (UV-vis), and Bomb calorimeter. The results showed that the yield of extracted lignin increased with the extraction time and power of the microwave. In addition, the extraction yield with ethanol was higher than the yield with isopropanol. The highest yield was 6.26 wt.%, with ethanol, 30 min extraction time, and 200 W microwave power.