Research evaluating the impact of alkali pretreatment of rape straw on the effectiveness of enzymatic hydrolysis of polysaccharides was carried out. The experiments were planned using Statistica program – a Box-Behnken design. The pretreatment conditions tested were: temperature 60–80ºC, reaction time 2–8 h and alkali (NaOH or Ca(OH)2) proportion 0,05–0,2 g ⋅ g-1 d.m. of substrate. The effectiveness of the used methods was evaluated on the basis of the amount of reducing sugars released during subsequent 48-hour enzymatic hydrolysis. The optimization conducted based on reducing sugars concentration indicated the following pretreatment conditions: NaOH in the proportion 0,15 g ⋅ g-1 d.m. of substrate, temperature 72ºC, time 6,6 h and Ca(OH)2 in the proportion 0,141 g ⋅ g-1 d.m. of substrate, temperature 74oC, time 3,2 h, which allowed to obtain reducing sugars concentration in hydrolysates 30,4 and 27,7 g ⋅ dm-3, respectively.
UV mutagenesis was used to obtain Gluconacetobacter xylinus mutants. The aim of this study was to attain a mutant able to produce high concentration of dihydroxyacetone. Exposure times were set to: 30, 45, 60 and 90 seconds. Mutants were isolated. The biotransformation of glycerol to DHA with use of these mutants was detected spectrophotometrically at 550 nm. The most active mutants was synthesizing 18,00 mg DHA ⋅ cm-3, what was 32% DHA ⋅ cm-3 more than the wiled type strain.
Indigenous bacteria in the natural environment can product a wide range of metabolites more efficiently. The aim of this work was to isolate from the natural environment non-pathogenic Clostridium strains that are able to convert glycerol to 1,3-propanediol and other metabolites of potential uses in industry. The effective methods of selection and maintenance of anaerobic cultures in the laboratory conditions were also investigated. Samples were pre-cultured on modified PY medium consisted 50 g/l of glycerol. Isolated colonies growth on TSC medium were screened on the basis of morphological characters typical for Clostridium sp. Isolated bacterial strains were allowed to growth in selective media such as RCM and modified PY. The metabolites of bacteria were investigated by the HPLC technique. The bacteria strains were identified by 16S rRNA technique. The highest percentage of isolates of the genus Clostridium were obtained from excrements of animals, compost, and silages. Nearly 60% were able to convert glycerol to 1,3-propanediol. The highest capacity for utilization of glycerol to 1,3-propanediol was observed in case of the species of Clostridium bifermentans and Clostridium sordelli. The most of examined microflora were also able to short-chain organic acids and ethanol synthesis.
