AbstractŠárka E., Kruliš Z., Kotek J., Růžek L., Korbářová A., Bubník Z., Růžková M. (2011): Application of wheat B-starch in biodegradable plastic materials. Czech J. Food Sci., 29: 232-242.Food application of wheat B-starch comprising small starch granules as a result of lower quality is problematic. Accordingly, B-starch or acetylated starch prepared from it, with the degree of substitution (DS) of 1.5-2.3, was used in biodegradable films after blending with poly-(ε-caprolactone) (PCL). The following mechanical characteristics of the produced films were derived from the stress-strain curves: Young modulus, yield stress, stress-at-break, and strainat-break. Water absorption of PCL/starch (60/40) films was determined according to European standard ISO 62. The measured data were compared with those of commercial A-starch. The films containing native starch degraded in compost totally during 2 months. Acetylation of starch molecules in the composites reduced the degradation rate. Optical microscopy, in combination with the image analysis system NIS-Elements vs. 2.10 completed with an Extended Depth of Focus (EDF) module, was used to study the surface morphology of PCL/starch films after 20-day and 42-day compost incubation. Chemical changes in the compost used for the film exposition were measured.

Tested soils (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002) were defined by chemical, textural and microbial characteristics. From the tests which describe cambisols, the following parameters have to be stressed. The higher level of C org (1.20-1.76%), which resulted in quite high microbial biomass carbon content (396-625 µg/g dry soil), high control respiration (0.45-0.80 mg CO 2 /h/ 100 g dry soil) and potential nitrification with (NH 4 ) 2 SO 4 (6.7-18.4 mg N-NO 3 /8 days/100 g dry soil). Studied luvisols reached typical levels: C org (0.97-1.22%), C MB (398-503 µg/g dry soil), control respiration (0.46-0.57 mg CO 2 /h/100 g dry soil), potential nitrification with (NH 4 ) 2 SO 4 (3.2-9.9 mg N-NO 3 /8 days/100 g dry soil). Lower levels of organic carbon and a medium level of microbial biomass raised in higher ratio C MB /C org (average 4.0%). Highly significant differences (p < 0.01) between cambisols and luvisols were determined for C org , N t , pH(KCl), C MB , C MB /C org , C E , control respiration and potential nitrification, while the difference in potential ammonification with peptone was at level p < 0.05. With the exemption of ratio C MB /C org all cambisol characteristics were higher than luvisol ones. Studied soils were evaluated by six biological criteria (C MB ; ratios: C MB /C org , C E /C MB , potential/control respiration, potential/ control ammonification, potential/control nitrification). These criteria distinguished tested soils into three groups. The first one includes two localities in the mountain region (Červená Voda 809, 810; altitude 565-590 m) defined as stagnic cambisols with higher content of C org (1.40, respective 1.76%) and simultaneously with the highest biomass of micro-organisms from all tested soils (C MB , 625, respective 621 µg/g dry soil). It is not surprising that microbial activities (respiration, nitrification) at these localities were also high. The majority of the studied localities (one eutric cambisol and four luvisols) belongs to the medium group. The third group includes two localities (Neumětely -haplic luvisol, Čistá u Rakovníka -eutric cambisol) where biological criteria was mostly the worst. In the period 1993-2002 microbial biomass carbon was for both sites in the range of 357-458 µg/g dry soil which are not so bad values, but in comparison with localities in mountain wet region they are low. This status was issued in the lower ratio C MB /C org (2.71-3.77%).

This article compares reclaimed soils in the Rhineland lignite mining area, Germany (RA) and in the north Bohemian brown coal basin, Czech Republic (NBB). Because of highly significant differences of physical and chemical characteristics (RA was characterized by lower content of sand, clay, soil organic carbon, and total nitrogen) between both analyzed areas, the content of microbial biomass carbon (CMB) differs significantly (p < 0.01): RA: 241.17 ± 96.50 μg C/g dry soil; NBB: 424.42 ± 136.23 μg C/g. Extracellular microbial carbon (CEX) was also significantly higher in RA than NBB. The measured CMB values from both mining areas were verified using two empirical mathematical models. Because our former model (used for evaluation of NBB) did not fit soils with low organic carbon content (0.10–0.80%), a new model was proposed. For evaluation of RA reclaimed sites the measured, model‐predicted, and calculated values were used. The best site in RA was Dürwiss Deponie (site 18 near Eschweiler), reclaimed in 1965 and characterized by good soil physical parameters (sand 4%, silt 77%, and clay 19%). In NBB undisturbed soils were the best, together with the site of Úžín (site 2 near Ústí and Labem), reclaimed in 1964, where high‐quality reclamation management resulted in high biological activity. According to biological criteria, the best management practice in NBB was use of high‐quality loam overlaying montmorillonite clayey subsoil. In RA direct reclamation of high‐quality loess with low content of sand also gave good results.

Cambisols, luvisols and Stagnosols are main soil taxonomical units covering 78% of the total area of the Czech republic. in the period 2001-2008 soil samples from 13 arable and 2 grassed localities were collected and tested. Microbial biomass carbon (MBC) was determined using microwave irradiation method (MW), chloroform fumigation extraction method (FE) and re-hydration technique (rHD). Soil samples were moistened, according to the content of organic carbon (C org ), by deionized water addition (%C org × 0.19 ml/g DM -dry mass of soil) immediately before MBC determination. Microwave sterilization (800 J/g DM = 600 W, 2 × 67 s, 100 g DM (10 soil samples) and microwave soil extracts digestion (800 J/ml = 250 W, 77 s, 24 ml) give the lowest values of MBC (204 ± 67 mg/kg DM; 100%) in comparison with FE (236 ± 57 mg/kg DM; 116%) and rHD (478 ± 138 mg/kg DM; 235%), respectively. High significant correlation (r = 0.9713) was found between tC (total carbon; 1.36 ± 0.29%) and tn (total nitrogen; 0.15 ± 0.03%) determined by CnS analyzer. Furthermore, high significant correlations were found between MBC-MW and MBC-rHD (r = 0.8965) as well as MBC-FE and DHa (dehydrogenase activity; r = 0.8094), respectively. DHa in studied soils reached 147 ± 68 mg of triphenylformazan/kg DM/24 h. C org formed 96% of tC and total Kjeldahl nitrogen 97% of tn, respectively. according our results MW is fully acceptable for MBC determination.

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