Safety evaluation of certain food additives
tải về 1.44 Mb. Chế độ xem pdf
|
| 1.
EXPLANATION At the request of the Codex Committee on Food Additives at its fortieth session (FAO/WHO, 2008), the Committee evaluated the enzyme branching glycosyltransferase (1,4- Į-glucan branching enzyme; Enzyme Commission number 2.4.1.18), which it had not evaluated previously. Branching glycosyltransferase catalyses the transfer of a segment of a 1,4- Į-D-glucan chain to a primary hydroxy group in a similar glucan chain to create 1,6-linkages. The enzyme is intended for 3 4 4 4 4 5 5 5 6 6 7 7 7 7 7 8 8 8 9 - 3 - use in starch processing to obtain modified starch with an increased number of branch points and improved functional properties. 1.1 Genetic modification Branching glycosyltransferase is manufactured by pure culture fermentation of a genetically modified strain of Bacillus subtilis containing a synthetic gene coding for branching glycosyltransferase from Rhodothermus obamensis. Bacillus subtilis is a Gram-positive bacterium that is widely distributed in nature and is considered to be non-pathogenic and non-toxigenic. It has a long history of use in the production of enzymes used in food processing, including enzymes from genetically engineered strains. It has also been granted a Qualified Presumption of Safety status by the European Food Safety Authority (2008). The gene encoding branching glycosyltransferase was originally cloned from R. obamensis, a thermophilic bacterium that was isolated from a marine hydrothermal vent. Based on the amino acid sequence of branching glycosyltransferase translated from the R. obamensis gene, a synthetic gene was designed that encodes branching glycosyltransferase with the same amino acid sequence as that of the native R. obamensis enzyme. The gene was subsequently placed under deoxyribonucleic acid (DNA) regulatory sequences derived from several Bacillus species and introduced into the B. subtilis host strain JA1343 by transformation. The chloramphenicol resistance gene (cat) was used in transformation as a selectable marker, but it was subsequently deleted to make the production strain marker free. tải về 1.44 Mb. Chia sẻ với bạn bè của bạn:
|