摘要:
On décrit une composition d'un moût de xanthane préparée à partir d'un milieu de culture renfermant en particulier au moins une source de soufre de concentration comptée en élément soufre au plus égale à 60 mg par litre de milieu de culture et d'au moins une souche du genre Xanthomonas , et d'une source de protéines dans un rapport pondéral protéines sur xanthane compris entre 0,05 et 2. Le moût récupéré contenant de préférence les cellules, à pH alcalin et en présence de cations bivalents, avec les protéines, constitue une composition qui manifeste des propriétés de thixotropie. Application de la composition dans un fluide de forage pour le forage des puits.
摘要:
A fermentation process for the production of a product comprising mannose units eg. xanthan gum in which a simple sugar is a component of the fermentation feedstock and a part of that sugar is mannose. Preferably the sugar is a mixture of mannose and glucose optionally containing minor amounts of other sugars, the mixture of mannose and glucose suitably being produced by the epimerisation of glucose.
摘要:
Variant xanthan gums, including non-acetylated, non-pyruvylated, non-acetylated and non-pyruvylated, and fully-acetylated xanthan gums. In addition, in vitro and in vivo methods for the synthesis of these gums are disclosed. Mutant Xanthomonas campestris strains useful in these synthesis are also specified.
摘要:
Compositions are provided which include a water-soluble polysaccharide polymer having a D-glucose:D-mannose:D-glucuronic acid ratio of about 2:2:1. The D-glucose moieties are linked in a beta-[1,4] configuration. The inner D-mannose moieties are linked in an alpha-[1,3] configuration, generally to alternate glucose moieties. The D-glucuronic acid moieties are linked in a beta-[1,2] configuration to the inner mannose moieties. The outer mannose moieties are linked to the glucuronic acid moieties in a beta-[1,4] configuration. Processes for preparing the polysaccharide polymers are also provided.
摘要:
Polysaccharide is produced by a single stage continuous culture of Xanthomonas bacteria, especially of the Xanthomonas campestris group, in a chemically defined culture medium having a growth limiting nutrilite which is a nitrogen source selected from glutamic acid, asparagine, a glutamate salt or an asparagine salt. During the continuous process the culture has a mean residence time in the culture vessel of 16 hr 2/3 or less, preferably between 9 and 16 hr 2/3. The use of glutamic acid, asparagine, glutamate salt or asparagine salt as the limiting nitrogen nutrilite increases the output of polysaccharide at mean residence times of 16 hr 2/3 and below, when compared with the outputs achieved using inorganic nitrogen sources at the same mean residence times.
摘要:
Procédé d'obtention d'une masse de microorganismes, producteurs de polysaccharides, qui consiste à faire multiplier les microorganismes dans un milieu contenant une enzyme qui hydrolyse le polysaccharide formé. Application dans un procédé de production de polysaccharide en deux étapes, dans lequel la phase croissance a lieu en présence de l'enzyme, notamment pour la production de scléroglucane par les champignons du genre Sclerotium .
摘要:
For the fermentative preparation of polysaccharides, in particular xanthane, water, production medium (sugars, nutrient salts), and an inoculation material of a suitable aerobic bacterium are mixed in a reactor as reaction components, the production medium being exposed to fermentation while an oxygen-containing gas is being supplied. The object is to avoid the usual low yield of such a process and to reject an expensive and sensitive alternative construction (circulation tube). According to the invention, the reaction components are introduced into a reactor vessel in a circulating flow by means of pumping means, which circulating flow comprises a rising flow and a descending flow which are separated from each other by one or more partitions disposed in the reactor vessel. The mixing is brought about because the rising flow and/or the descending flow is passed essentially in the form of a plug flow through one or more static in-line mixers.
摘要:
A method of increasing xanthan gum production, comprising culturing a Xanthomonas campestris strain having a xanthan-increasing modification in a culture medium, wherein the modification is selected from the group consisting of (1) a mutation causing rifampicinresistance; (2) a mutation causing bacitracin-resistance; or (3) exogenous genetic information controlling the synthesis of xanthan; and separating xanthan from the culture medium, is provided along with specific DNA sequences and Xanthomonas campestris strains showing increased xanthan gum production.