Thermomyces lanuginosus STm: A source of thermostable hydrolytic enzymes for novel application in extraction of high-quality natural rubber from Taraxacum kok-saghyz (Rubber dandelion)

Abstract

Hydrolytic enzymes from a newly isolated strain of the thermophilic fungus Thermomyces lanuginosus were used to extract rubber from Taraxacum kok-saghyz commonly known as rubber (or Russian or Kazak(h)) dandelion. The fungus was isolated from garden soil and identified as Thermomyces lanuginosus STm based on 18S rRNA gene sequence analysis. The isolate produced considerable amounts of extracellular hydrolytic enzymes on lignocellulosic substrates at 55°C incubated for 8days in 150mL shake flask experiments. The maximum enzyme activities on wheat straw and guayule bagasse were: xylanase (167.41; 130.1U/mg), inulinase (69.8; 34.1U/mg), cellulase (carboxymethyl cellulase) (16.7; 4.8U/mg), filter paper assay (FPase) (14.2; 5.5FPUg−1) and pectinase (7.2; 3.2U/mg), respectively. In addition, alkali-pretreated roots of Taraxacum kok-saghyz (TK), incubated with crude enzyme extracts from T. lanuginosus STm grown on guayule bagasse, subsequently yielded more natural rubber (90mg/g dry TK root) than previously established protocols, Eskew process (24mg/g) and commercial-enzyme-combination process (45mg/g). Rubber purity in the T. lanuginosus STm treatment was 71.7%, greater than the Eskew process at 37.5%. However, the crude T. lanuginosus STm enzyme treatment at 91.6% rubber purity approached the purity of the commercial-enzyme-combination process at 94.1% purity.