1.
Cellulase deactivation based kinetic modeling of enzymatic hydrolysis of steam-exploded wheat straw.
Zhang, Y, Xu, JL, Xu, HJ, Yuan, ZH, Guo, Y
Bioresource technology. 2010;(21):8261-6
Abstract
Applying mass action law and quasi-steady-state theory, two cellulase kinetic models namely Eqs. (5) and (8) were developed on the basis of the first and second order reactions of enzyme deactivation, respectively. The two models are compared according to analysis of experimental data from enzymatic hydrolysis steam-exploded wheat straw. Both simulation and prediction results show Eq. (8) has much higher accuracy than Eq. (5). Analysis of initial hydrolysis rate is also in accordance with Eq. (8) and against Eq. (5). Fitted values of k(2) (the rate constant of product formation), k(de2) (the rate constant of enzyme deactivation) and K(e) (the equilibrium constant) determined from Eq. (8) are 0.4732 h(-1), 0.4011 L/(hg), and 16.8597 g/L, respectively. The higher the enzyme concentration is, the larger the deactivation rate.
2.
[Spatial variability of farmland soil nutrients at Taihang piedmont].
Zhang, Y, Mao, R, Hu, C, Zhang, J, Zhu, A
Ying yong sheng tai xue bao = The journal of applied ecology. 2004;(11):2049-54
Abstract
By the method of geostatistics, this paper studied the spatial variability of soil nutrients in 30,490 hm2 crop field in Luancheng region and in 15 hm2 experimental field in Luancheng Ecological Agriculture Station of Chinese Academy of Sciences. The results showed that the variation of soil nutrient contents differed obviously, and the semivariograms could be simulated by Gaussian and spherical models with some nugget variances. The limit distance of spatial correlation was 4.2-15.6 km and 112-223 m in Luancheng region and in experimental field, respectively, and the spatial variability of soil organic matter, N, P and K was of semivariance structure. It revealed that there existed a spatial correlation in soil nutrient contents under relatively large-block scale, which made it possible to develop regionalized soil nutrient precision management.