ENZYMATIC SYNTHESIS AND CHARACTERIZATION OF A NEW TRISACCHARIDE, α-LACTOSYL-β-FRUCTOFURANOSIDE

Computational prediction of the bioactivity potential of proteomes based on expert knowledge

Advances in the field of genome sequencing have enabled a comprehensive analysis and annotation of the dynamics of the protein inventory of cells. This has been proven particularly rewarding for microbial cells, for which the majority of proteins are already accessible to analysis through automatic metagenome annotation. The large-scale in silico screening of proteomes and metaproteomes is key to uncover bioactivities of translational, clinical and biotechnological interest, and to help assign functions to certain proteins, such as those predicted as hypothetical. This work introduces a new method for the prediction of the bioactivity potential of proteomes/metaproteomes, supporting the discovery of functionally relevant proteins based on prior knowledge. This methodology complements functional annotation enrichment methods by allowing the assignment of functions to proteins annotated as hypothetical/putative/uncharacterised, as well as and enabling the detection of specific bioactivities and the recovery of proteins from defined taxa. This work shows how the new method can be applied to screen proteome and metaproteome sets to obtain predictions of clinical or biotechnological interest based on reference datasets. Notably, with this methodology, the large information files obtained after DNA sequencing or protein identification experiments can be associated for translational purposes that, in cases such as antibiotic-resistance pathogens or foodborne diseases, may represent changes in how these important and global health burdens are approached in the clinical practice. Finally, the Sequence-based Expert-driven pRoteome bioactivity Prediction EnvironmENT, a public Web service implemented in Scala functional programming style, is introduced as means to ensure broad access to the method as well as to discuss main implementation issues, such as modularity, extensibility and interoperability.

Efficient Biosynthesis of Lactosucrose from Sucrose and Lactose by the Purified Recombinant Levansucrase from Leuconostoc mesenteroides B-512 FMC

Lactosucrose, a rare trisaccharide formed from sucrose and lactose by enzymatic transglycosylation, is a type of indigestible carbohydrate with a good prebiotic effect. In this study, lactosucrose biosynthesis was efficiently carried out by a purified levansucrase from Leuconostoc mesenteroides B-512. The target gene was cloned and expressed in Escherichia coli, and the recombinant enzyme was purified to homogeneity by nickel affinity and gel filtration chromatography. The effects of pH, temperature, substrate concentration, substrate ratio, and enzyme amount on lactosucrose biosynthesis were studied in detail, and the optimized conditions were determined to be pH 6.5, 50 °C, 27% (W/V) sucrose, 27% (W/V) lactose, and 5 U mL(-1) of the purified recombinant enzyme. Under the optimized reaction conditions, the maximal lactosucrose yield reached 224 g L(-1) after reaction for 1 h. Therefore, L. mesenteroides levansucrase could be considered a potential candidate for future industrial production of lactosucrose.

Synthesis of novel bioactive lactose-derived oligosaccharides by microbial glycoside hydrolases

Prebiotic oligosaccharides are increasingly demanded within the Food Science domain because of the interesting healthy properties that these compounds may induce to the organism, thanks to their beneficial intestinal microbiota growth promotion ability. In this regard, the development of new efficient, convenient and affordable methods to obtain this class of compounds might expand even further their use as functional ingredients. This review presents an overview on the most recent interesting approaches to synthesize lactose-derived oligosaccharides with potential prebiotic activity paying special focus on the microbial glycoside hydrolases that can be effectively employed to obtain these prebiotic compounds. The most notable advantages of using lactose-derived carbohydrates such as lactosucrose, galactooligosaccharides from lactulose, lactulosucrose and 2-α-glucosyl-lactose are also described and commented.

Lactosucrose production by various microorganisms harboring levansucrase activity

Production of the artificial sweetener, lactosucrose, by various microorganisms containing levansucrase activity was investigated. Of the tested bacteria, Bacillus subtilis was the most effective producer using lactose as an acceptor and sucrose as a fructosyl donor. Lactosucrose production by this strain was optimal at pH 6.0 and 55 degrees C whereupon 181 g lactosucrose l(-1) was produced from 225 g lactose l(-1) and 225 g sucrose l(-1) in 10 h.

Screening of sugars inhibitory against sucrose-dependent synthesis and adherence of insoluble glucan and acid production by Streptococcus mutans

Various sucrose derivatives and a sucrose analogue were enzymatically synthesized on the assumption that structural similarities of the sugars to sucrose would endow them with an ability to inhibit the cariogenicity of sucrose. The effect of these sugars on sucrose-dependent synthesis and adherence of insoluble glucan and on acid fermentation of sucrose by Streptococcus mutans was examined in vitro. Although none of them inhibited the acid fermentation, several sugars not only inhibited the synthesis and adherence of insoluble glucan, but were themselves only slightly fermented as well.