Degradation of Rice Husks by Fungi Species Isolated from Rice Husk Dumps at Abakaliki

Abstract Degradation of rice husks by fungi species isolated from old rice husk dumps at Abakaliki rice mill was carried out. Standard microbiological techniques were used in isolating and identifying the fungi species from the old rice husk dumps. The isolated fungi species were used to screen for their ability to degrade fresh rice husks by their ability to produce reducing sugars. The identified fungi isolates were then used to degrade fresh rice husks for five days. Also, the cellulase activities of the fungal species that degraded the rice husks were assessed for their ability to produce clear zones on carboxylmethylcellulose (CMC) agar. Results showed that ten species of fungi were isolated, out of which five were able to produce reducing sugars and were identified as Aspergilus flavus, Aspergillus niger, Aspergillus fumigatus, Rhizopus microsporus and Mucor pusillus. The result revealed that Mucor pusillus degraded the rice husks more by producing the highest reducing sugar value of 123.342 mg/l followed by Aspergilus flavus (116.551mg/l), Aspergillus fumigatus (96.731mg/l), Rhizopus microsporus (94.225mg/l) and Aspergillus niger (93.153mg/l). The highest reducing sugar production occurred on the 3rd and 4th days of degradation. With respect to cellulase activity, Mucor pusillus had the highest cellulase activity by producing the widest clear zone of 40.00mm on CMC agar while Aspergillus niger had the least cellulase activity by producing the smallest clear zone of 24.0mm in CMC agar. Therefore, the production of reducing sugars by these organisms showed that they can degrade rice husks.