Xylan degradation by different xylanases of rumen bacterium Pseudobutyrivibrio xylanivorans Mz5T | Razgradnja ksilana z različnimi ksilanazami vampne bakterije Pseudobutyrivibrio xylanivorans Mz5T

anglais. The use of xylanases as feed additives for monogastric animals is very promising. Many experiments have proved their beneficial effect on animal health and performance. A new rumen bacterium species has recently been isolated: P. xylanivorans, type strain Mz5T, which has a very high xylanolytic activity. Some of its xylanolytic enzymes have already been described. We want to analyse the rest of them to find the reason for its high xylanolytic activity and to assess the possibilities of using this bacterium as a probiotic for monogastric animals (pigs, poultry) or its enzymes as feed additives. We have partially isolated two xylanases from the cell extract: 44 kDa and 81 kDa and examined their properties. We also compared enzyme activities of cell surface xylanases with xylanases in cell extract. The 44 kDa xylanase is an exoxylanase without β-xylosidase activity. We assume that the 81 kDa xylanase is an endoxylanase. Xylanolytic enzymes on the cell surface are efficient xylan degraders, but they are unable to degrade xylobiose. Xylobiose is degraded by xylanolytic enzymes inside the cell.

slovène. Uporaba ksilanaz kot krmnih dodatkov je pri monogastričnih živalih zelo obetavna, saj so njihov ugoden učinek na zdravstveno stanje in prirast živali potrdile številne raziskave. Pred kratkim je bila opisana nova vrsta vampne bakterije P. xylanivorans s tipskim sevom Mz5T, ki je močno ksilanolitična. Nekaj njenih ksilanolitičnih encimov je že opisanih, preiskati pa želimo še ostale, da bi ugotovili vzrok visoke ksilanolitične aktivnosti in možnosti uporabe bakterije kot probiotika pri monogastričnih živalih (prašiči, perutnina) ali encimov kot krmnih dodatkov. Iz celičnega izvlečka smo uspeli delno očistiti ksilanazi, veliki 44 kDa in 81 kDa in delno proučiti njuno encimsko delovanje. Primerjali smo tudi encimsko delovanje na celično površino vezanih ksilanaz s ksilanazami celičnega izvlečka. 44 kDa ksilanaza je eksoksilanaza brez β-ksilozidazne aktivnosti, pri ksilanazi velikosti 81 kDa predvidevamo, da gre za endoksilanazo. Ksilanolitični encimi celične površine učinkovito razgrajujejo ksilan, vendar niso sposobni cepiti ksilobioze. Le-to razgradijo ksilanolitični encimi v notranjosti celice.