Alina Krystynowicz

Factors affecting the yield and properties of bacterial cellulose.

Acetobacter xylinum E25 has been applied in our studies in order to find optimal culture conditions for effective bacterial cellulose (BC) production. The strain displays significantly higher stability in BC production under stationary culture conditions. In contrast, intensive agitation and aeration appear to drastically reduce cellulose synthesis since such conditions induced formation of spontaneous cellulose nonproducing mutants (Cel−), which dominated in the culture. Mutation frequency strictly depends on the medium composition in agitated cultures. Enrichment of the standard SH and Yamanaka media with 1% ethanol significantly enhanced BC production in stationary cultures. Horizontal fermentors equipped with rotating discs or rollers were successfully applied in order to improve culture conditions. Relatively slow rotation velocity (4 rpm) and large surface area enabling effective cell attachment are optimal parameters for cellulose production. Physical properties of BC samples synthesized either in stationary cultures or in a horizontal fermentor revealed that cellulose from stationary cultures demonstrated a much higher value of Youngs modulus, but a much lower value of water-holding capacity. Journal of Industrial Microbiology & Biotechnology (2002) 29, 189–195 doi:10.1038/sj.jim.7000303

Complete genome sequence of Gluconacetobacter xylinus E25 strain—Valuable and effective producer of bacterial nanocellulose ☆

This study reports the release of complete genome sequence of the producer of bacterial nanocellulose (BNC) - Gluconacetobacter xylinus E25, a vinegar-isolated strain. Preliminary sequence analysis revealed complexity of the genome structure and familiarized genetic basis of productive properties of E25 strain. The genome consists of one chromosome and five plasmids. Whole genome sequencing has opened up new perspectives for further bioinformatics and experimental studies allowing the elucidation of molecular mechanisms responsible for regulation of production of BNC - a valuable biomaterial.

Mathematical modelling of ester synthesis by lipase in biphasic system

Abstract The invented mathematical model of ester synthesis in a biphasic system using the immobilised Mucor circinelloides lipase, situated in organic phase, was experimentally verified by butyl oleate, oleyl oleate, sucrose oleate and sucrose caprylate synthesis. The model took into consideration the fact revealed in experiments that water being a by-product of a reaction, created a separate phase thus influencing a value of equilibrium constant in the organic phase (KO). The applied mathematical model makes it possible to determine with high accuracy the yield of ester synthesis that can be obtained in the reaction poststational state.

Activity of immobilised in situ intracellular lipases from Mucor circinelloides and Mucor racemosus in the synthesis of sucrose esters

The activity of intracellular, immobilised in situ lipases from Mucor circinelloides and Mucor racemosus can be changed by means of chemical modifications of the reaction milieu, using some substances isolated from Mucor cells. The substances act ambivalently (as activators or inhibitors) on the lipases. The yield of sucrose monocaprylate synthesis and the time to reach the reaction equilibrium state were determined in mono- and biphasic systems. The investigations proved that in a milieu of di-n-pentyl ether saturated with water, 92% of sucrose was esterificated, and the location of the lipase on the interface between the phases, markedly diminished the time equilibrium to reach.

Application of bacterial cellulose for clarification of fruit juices

The aim of our studies was to estimate the usefulness of bacterial cellulose synthesised by Acetobacter xylinum E25 for the clarification of apple juice. The cellulose was applied either as a membrane formed under stationary culture conditions or as a suspension obtained by disintegration of such a membrane. The membrane was used as a filter bed. The results of our studies confirm that cellulose membranes may be used as filtration ones. After filtration through cellulose membranes, apple juice displayed very high clarity, higher than its sample clarified under standard conditions, even after a stability test. Juice clarification only by filtration through cellulose membrane does not assure its stable colour, which darkens under the conditions of a stability test performance. This phenomenon is also observed for other products clarified by filtration only. Bacterial cellulose application as an adsorbent for fruit juice clarification yielded the product with demanded stability.