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Flavonols contribute to the red color displayed by the anthocyanins through intermolecular co-pigmentation [8]. Intermolecular co-pigmentation of anthocyanins with other compounds increases the color intensity and causes the wavelength of maximum absorbance to shift toward higher wavelengths (bathochromic shift). In addition, because flavonols have strong UV absorbance, these pigments play important protective functions against damaging effects of UV radiation [9].
A major advantage with anthocyanins and flavonols for their use as natural dyes is the fact that they have attached sugar groups, which can be removed without loss of their colors. The chemical group freed after removal of sugars could then be used to attach these dyes with cellulose in fibers. Description of Research Two kinds of primary species, American Cranberry plant tissue and two fungal species, Curvularia lunata and Curvularia pallescens, can be used in natural growth media to produce dyes or dye precursors. The technology is simple to implement two steps:
(i) Grow the primary species in the laboratory or in a bioreactor with the right growth medium,
(ii) Harvest the dye or dye precursors from the plant or fungal cells.
We have successfully established cranberry cell culture system from cranberry (Vaccinium macrocarpon, Ericaceae) stems, leaves and leafstalks by using Gamborgs B5 medium containing 5 mM 1- naphthaleneacetic acid (NAA), 5 M 2,4-di-chlorophe-noxy acetic acid (2,4-D), and 2.5 mM kinetin at 25oC in the dark.
Production of Pigment from Cranberry Callus
Production of flavonoids in cranberry callus varies under different stresses such as light irradiation (red light of 660 nm and far-red light of 730 nm), temperature-changing (from 25oC to 4oC, or 37oC), and wounding.
Cranberry callus produces anthocyanins only on exposure to light. Production of anthocyanins in
cranberry callus was induced under continuous light irradiation. However, because anthocyanin is
red color, it was observed that only top layer of the callus, which received light produces
anthocyanins.
Production of Pigment from Cranberry Cell Suspension
Although callus provides more accessible uniform cells than the intact plant, the callus tissue is not uniform since only the base of the callus is exposed to the medium and the callus mass may contain cells at various stages of development. The alternative approach is to use cell suspensions. Cell suspensions show a faster growth rate, and all cells are exposed uniformly to the medium, and environment such as light. Cell suspensions are preferred for large scale and commercial production of secondary metabolic products.
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