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Optimization of Culture Conditions for the Production of Xylanase by Two Thermophilic Fungi Under Solid State Fermentation

KUMKUM AZAD
Department of Botany, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh

MD. ABDUL HALIM
Department of Botany, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh

FEROZA HOSSAIN
Department of Botany, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh

Abstract/ Executive Summary:

Two thermophilic fungi, Thermomyces lanuginosus BPJ-10 and Rhizomucor pusillus BPJ-2 were studied under solid state fermentation (SSF) using wheat bran for the production of thermostable xylanase. The optimum time required for the production of xylanase was found to be 4 days and 7 days for R. pusillus BPJ-2 and T. lanuginosus BPJ-10 respectively. The optimum temperatures for the production of xylanase by R. pusillus BPJ-2 and T. lanuginosus BPJ-10 were 45°C and 50°C respectively. The maximum activity of xylanase (1.685 IU/ml and 0.075 IU/ml) was exhibited by T. lanuginosus BPJ-10 and R. pusillus BPJ-2 at pH 7.0 and pH 4.0 respectively. The optimum moisture content for maximum xylanase production was 90% for both fungi.

Keywords: Xylanase, Thermophilic fungi, Thermomyces lanuginosus and Rhizomucor pusillus

Location: Department of Botany, Jahangirnagar University, Savar, Dhaka

Start Date: 00-00-2013

End Date: 00-00-2013

Program Area: Pest Management

Commodity: Fortified food

Objectives:

1. To investigate two thermophilic fungi, Thermomyces lanuginosus BPJ-10 and Rhizomucor pusillus BPJ-2 for the production of thermostable xylanase to optimize some of the cultural parameters such as temperature, pH, incubation time and moisture content under solid state fermentation for maximization of the production of enzymes.

Methodology:

Two thermophilic fungi, Thermomyces lanuginosus BPJ-10 and Rhizomucor pusillus BPJ-2 were isolated and identified at the laboratory of Plant Physiology and Biochemistry, Department of Botany, Jahangirnagar University, Savar, Dhaka. The fungi were cultured on PDA media and maintained at 50°C and 45°C temperature for T. lanuginosus BPJ-10 and R. pusillus BPJ-2 respectively. The cultures were incubated for five days and the spores of the cultures were washed with sterile water and the resulting suspention (2.5 × 105 spores per ml) was used as inocula. These fungi were employed for the production of xylanase under solid state fermentation. To optimise the enzyme production following cultural conditions were investigated by using wheat bran as a solid substrate. Wheat bran (10g) was taken in each of the 250 ml conical flask. The substrates were mixed thoroughly with distilled water for maintaining the suitable amount of moisture content. The flasks were then properly cotton plugged and autoclaved at 121°C for 15 minutes. Each flask was inoculated with 2 ml of spore suspension. To find the effect of temperature for maximization of enzyme production, inoculated flasks were incubated at temperature ranging from 35° to 60°C. To investigate the effect of incubation period for maximization of enzyme production, the inoculated flasks were incubated for 10 days at 45°C and 50°C for T. lanuginosus BPJ-10 and R. pusillus BPJ-2 respectively. Enzyme was extracted and assayed at every 24 hours starting from the 1st day upto 10th day of inoculation. For the determination of the effect of moisture content on enzyme production 50, 60, 70, 80, 90 and 100% distilled water were added with solid substrate. The pH of the initial culture was adjusted to 4, 5, 6, 7, 8 and 9 for both fungi to find its optimum value. After optimum incubation time (7 days for T. lanuginosus BPJ-10 and 4 days for R. pusillus BPJ-2) 100 ml of 1% NaCl solution was added to the culture and mixed properly to each fermented biomass. In order to disperse the mycelia bound biomass, the flasks with moldy substrate was shaken in a shaker for 45 minutes at 150 rpm. The fermented slurry was first filtered with nylon cloth and then extracts were filtered with Millipore membrane filter paper (0.25μ). Clear filtrate was obtained and centrifuged at 4500 rpm for 15 minutes. The clear supernatants were used for the determination of enzyme activity. The amount of reducing sugar was estimated by Dinitro salicylic acid (DNS) method. Xylanase activitiy was assayed by standard procedure. The enzyme activity was calculated and expressed in International Unit (IU). One IU is the amount of enzyme which liberates 1 μmol of reducing sugar per minute under assay conditions. The enzyme activities were measured from average of three replicates for each parameter. The relative percentage of xylanase activity was calculated by taking the maximum activity as 100%.

Source of Information: J. Asiat. Soc. Bangladesh, Sci. 39(1): 43-51, June 2013

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It may be concluded from the present findings that the thermophilic fungi, T. lanuginosus BPJ-10 and R. pusillus BPJ-2 have potential capability of producing xylanase under the physiological conditions and the cultural environment described above. Though both fungi exhibited maximum activity of xylanase in the same level of moisture content (90%), their level of temperature and pH were different. Moreover, R. pusillus BPJ-2 exhibited maximum activity of xylanase on 4th day of incubation whereas it was exhibited by T. lanuginosus BPJ-10 on 7th day of incubation, which reveals that R. pusillus BPJ-2 is more economical than that of T. lanuginosus BPJ-10 in the respect of time duration. Besides these, T. lanuginosus BPJ-10 is more potential thermophilic fungi than R. pusillus BPJ-2 with regard to xylanase producing capacity in solid state fermentation.

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