AIM:To investigate the impact of agitation speed on pectinase production and morphological changing of Aspergillus niger (A. niger ) HFD5A-1 in submerged fermentation.
METHODS:A. niger HFM5A-1 was isolated from a rotted pomelo. The inoculum preparation was performed by adding 5.0 mL of sterile distilled water containing 0.1% Tween 80 to a sporulated culture. Cultivation was carried out with inoculated 1 × 10 7 spores/mL suspension and incubated at 30 ℃ with different agitation speed for 6 d. The samples were withdrawn after 6 d cultivation time and were assayed for pectinase activity and fungal growth determination. The culture broth was filtered through filter paper (Whatman No. 1, London) to separate the fungal mycelium. The cell-free culture filtrate containing the crude enzyme was then assayed for pectinase activity. The biomass was dried at 80 ℃ until constant weight. The fungal cell dry weight was then expressed as g/L. The 6 d old fungal mycelia were harvested from various agitation speed, 0, 50, 100, 150, 200 and 250 rpm. The morphological changing of samples was then viewed under the light microscope and scanning electron microscope.
RESULTS:In the present study, agitation speed was found to influence pectinase production in a batch cultivation system. However, higher agitation speeds than the optimal speed (150 rpm) reduced pectinase Effect of agitation speed on the morphology of Aspergillus niger HFD5A-1 hyphae and its pectinase production in submerged fermentation
ORIGINAL ARTICLE
Basic StudyDarah Ibrahim, Haritharan Weloosamy, Sheh-Hong Lim production which due to shear forces and also collision among the suspended fungal cells in the cultivation medium. Enzyme activity increased with the increasing of agitation speed up to 150 rpm, where it achieved its maximal pectinase activity of 1.559 U/mL. There were significant different (Duncan, P < 0.05) of the pectinase production with the agitation speed at static, 50, 100, 200 and 250 rpm. At the static condition, a well growth mycelial mat was observed on the surface of the cultivation medium and sporulation occurred all over the fungal mycelial mat. However with the increased in agitation speed, the mycelial mat turned slowly to become a single circular pellet. Thus, it was found that agitation speed affected the morphological characteristics of the fungal hyphae/mycelia of A. niger HFD5A-1 by altering their external as well as internal cell structures.
CONCLUSION:Exposure to higher shear stress with an increasing agitation speed could result in lower biomass yields as well as pectinase production by A. niger HFD5A-1.
Core tip:We report the influence of agitation speed on pectinase production on our newly isolate Aspergillus niger (A. niger ) HFM5A-1 in submerged fermentation.The agitation speed was found to influence pectinase production in a batch cultivation system. However, higher agitation speeds than the optimal speed (150 rpm) reduced pectinase production which due to shear forces and also collision among the suspended fungal cells in...
The bacterium, Enterobacter aerogenes NBO2 was cultivated in 250 ml Erlenmeyer flask under submerged fermentation and physiochemical characteristics were studied in order to improve the pectinase production. Fermentation condition improved were pH 6.5, cultivation temperature of 37°C, inoculums size of 3% (v/v) 7.4x10 8 cell/ml and agitation speed of 250 rpm, together with pectin concentration of 1.50% (w/v) and 0.26% of yeast extract as carbon and nitrogen sources, respectively had produced the highest pectinase production of about 18.54 U/mL and 0.43 g/L cell growth at 24 hours incubation time. The enzyme production by this bacterial isolate was found not growth dependent. There were increment in enzyme production and cell growth after improvement of physical and chemical parameters.
Agitation speed was found to influence the tannase production and fungal growth of Aspergillus niger FETL FT3. The optimal agitation speed was at 200 rpm which produced 1.41 U/ml tannase and 3.75 g/l of fungal growth. Lower or higher agitation speeds than 200 rpm produced lower enzyme production and fungal growth. Based on the SEM and TEM micrograph observation, there was a significant correlation between agitation speed and the morphology of the fungal mycelia. The results revealed an increase of the enzyme production with the change of the fungal growth morphology from filamentous to pelleted growth forms. However, the exposure to higher shear stress with an increasing agitation speed of the shaker also resulted in lower biomass yields as well as enzyme production.
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