A quantitative bioassay specific for polygalacturonases

Enhancement of natural pigment extraction using Bacillus species xylanase

Pigment extracts from the root of Lithospermum erythrorhizon are used as natural red dyes, as well as basic drugs due to their numerous pharmacological activities. In recent years, the demand for such natural pigment materials has increased; however, in natural dye production, the pigment yield is strongly affected by the source of cultivation, extracting conditions, and solvents. Accordingly, this study proposes a method of enzymatic pigment production based on the introduction of hydrolytic enzymes prior to the usual extraction to avoid repeated pigment extraction. The matrix destruction in the epidermal layer of the root by the enzymes was found to improve the pigment extractability, that is, the increment of K(L), the mass transfer coefficient, representing the pigment mobility in the epidermal layer. The root tissue maceration by the hydrolytic enzymes was also measured to evaluate the pigment extractability, and a linear relationship was observed between the K(L) values and the tissue maceration up to the addition of 3000 units/g of xylanase, indicating that the enzymatic maceration proportionally increases the interfacial area between the pigment and the solvent. Bacillus sp. DX107 xylanase only served to increase the extractability of the pigment by loosening the root shell matrix, without affecting the contents and color properties of the pigment, as almost no difference was found in the color between the pigments extracted using xylanase and those extracted according to the traditional method.

Differential effect of site-directed mutations in pelC on pectate lyase activity, plant tissue maceration, and elicitor activity

Oligonucleotide site-directed mutations were introduced into the pelC gene of Erwinia chrysanthemi EC16 that directed single or double amino acid changes affecting disulfide linkages, calcium binding, catalysis, and protein folding. Subsequent characterization of the purified PelC mutant proteins demonstrated that pectinolytic function involves amino acids located near the calcium binding site rather than those surrounding an invariant vWiDH sequence. Wild-type PelC and the tested mutant proteins generally macerated plant tissue in proportion to their specific pectinolytic activity in vitro. However, some mutants gave higher maceration activity in plant tissue and elicited greater production of the phytoalexin, glyceollin, in soybean cotyledons than predicted by their in vitro pectinolytic activity. Most notable in this regard were three different mutations at lysine 172 with greatly reduced pectinolytic activity but as much elicitor activity as the wild-type protein. PelE macerated plant tissue 10 times more efficiently than PelC, as observed previously, but surprisingly showed equal activity in the elicitor assay. The results indicate that factors other than pectinolytic activity per se are involved in plant tissue maceration and elicitor activity.