Mucoadhesive improvement of alginate microspheres as potential gastroretentive delivery carrier by blending with Bletilla striata polysaccharide.

As polysaccharide from Bletilla striata (BSP) was anticipated with mucoadhesive improvement in sodium alginate (SA) microspheres, BSP was mixed with SA to construct a composite microsphere to retain in the gastrointestinal tract for a long time. The morphological properties, particle size and thermodynamic properties of the microspheres in combination with comprehensive evaluations in the swelling properties, mucin adsorption, ex vivo and in vivo gastric retention were determined to characterize the mucoadhesion of SA-BSP blend microspheres. Results showed that the prepared microspheres were discrete and spherical. The addition of BSP increased flexibility and reduced rigidity of SA microsphere. Furthermore, the swelling property, mucin adsorption ability and the retention rate on the gastric mucosa of SA matrix were increased after blending with BSP. Mucoadhesion tests showed the SA-BSP microspheres stayed much longer in rats' stomach than the SA microsphere did. Above all, the SA-BSP microspheres with the enhanced mucoadhesion suggested being a potential drug carrier in developing the gastroretentive drug delivery system.

[Construction of an ethanologenic Escherichia coli strain expressing beta-glucosidase].

Constructing ethanologenic strains with cellulose activity is important to achieve consolidated bioprocessing of lignocellulose for ethanol production. In this study, we integrated the pyruvate decarboxylase gene pdc and alcohol dehydrogenase gene adhB from Zymomonas mobilis ZM4 into Escherichia coli JM109 by Red recombination method to generatea recombinant strain E. coli P81 that could produce ethanol from glucose. Abeta-glucosidase gene bglB from Bacillus polymyxa 1.794 was cloned into the recombinant E. coli P81 and beta-glucosidase was expressed to give a new recombinant strain E. coli P81 (pUC19-bglB) with dual functions of cellobiose degradation and ethanol production. The extracellular beta-glucosidaseactivity was 84.78 mU/mL broth and the extracellular cellobiase activity of E. coli P81 (pUC19-bglB) was 32.32 mU/mL broth. E. coli P81 (pUC19-bglB) fermented cellobiose to ethanol with a yield of 55.8% of the theoretical value, and when glucose and cellobiose were co-fermented, the ethanol yield reached 46.5% of thetheoretical value. The construction of consolidated bioprocessing strain opens the possibility to convert cellobiose to ethanol in a single bioprocess.