Efficient retting of bast fiber yielding stems by extracellular enzyme conglomerate and oxalic acid produced by a newly isolated Penicillium sp.

In a screening program aimed at isolating a fungus capable of retting jute (Corchorus olitorius) and mesta (Hibiscus sabdariffa) ribbons within a short time, a fungus producing multiple extracellular enzymes such as polygalacturonase (83.28 IU/g), pectinolytic activity (42 IU/g), xylanase (117.96 IU/g), carboxymethylcellulase (9.81 IU/g) and oxalic acid (8.73mM) on wheat bran was isolated. The fungus was identified as Penicillium oxalicum on the basis of morphological characteristics. A significant feature is that xylanase activity increased >20 fold in solid state fermentation on wheat bran from that in submerged fermentation in minimal medium with birch wood xylan. Compatible pH and temperature optima of polygalacturonase and xylanase facilitated their joint action on the substrate. Thermostability of polygalacuronase , better than other strains of P.oxalicum aided in its functional capability. The boiled culture extract of P.oxalicum was found to remove significant amount of pectin from different portions of jute and mesta stem ribbons within 40h showing calcium chelating effect of oxalic acid. The culture extract possessing the functional enzymes and oxalic acid was able to remove 65-100% pectin from different portions of jute ribbons and 100% pectin from all portions of mesta ribbons releasing well separated fibres within 40h. The culture extract of the fungus on the sixth day of fermentation was able to ret whole jute and mesta ribbons within 40h producing well separated fibers.