A.B. Ariff¹* and C. Webb²

¹Department of Biotechnology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
²Department of Chemical Engineering, UMIST, P 0 Box 88, Manchester M60 IQD, United Kingdom

(Received 9 February 1998 / Accepted 15 May 1998)

Abstract.
Batch production of glucoamylase by Aspergillus awamori has been studied using different types and concentrations of carbon and nitrogen sources. The fermentations were carried out using an 81 stirred tank fermenter. An initial potato starch concentration of 50 g/l was found optimum for glucoamylase production. When (NH₄)₂SO₄ was used as the sole nitrogen source, irrespective of carbon concentration, an initial concentration of above 7.5 g/l repressed glucoamylase biosynthesis. On the other hand, yeast extract did not show any signs of repression, even though it was used at very high concentration (20 g/l). An initial concentration of yeast extract between 7.5 g/l and 10 g/l was found optimum in terms of yield based on cell mass (P_m/X_m). The addition of small amounts of yeast extract (1-2 g/1) into a medium containing (NH₄)₂SO₄ and starch at a balanced carbon to nitrogen (C/N) ratio increased glucoamylase production greatly. Using 50 g/l potato starch as a carbon source, the maximum glucoamylase concentration obtained using optimized concentration of (NH₄)₂SO₄ yeast extract and a mixture of them were 25.23, 48.77 and 49.62 U/ml, respectively.

Keywords: glucoamylase, Aspergillus awamori, medium optimization, C/N ratiobr

A Chellapandian¹ and C.A. Sastry²*

¹Department of Bioengineering, Institute of Biotechnology, UNAM, Apdo 510 3 Cuernavaca, Morelos 62271, Mexico.
²Institute of Advanced Studies, University of Malaya, 50603 Kuala Lumpur, Malaysia.

(Received 18 February 1998 / Accepted 26 February 1998)

Abstract.
The stability of neutral and alkaline proteases immobilized on hexamethylene diamine coated vermiculite by covalent linkage using bifunctional reagent glutaraldehyde were investigated. Immobilized proteases showed an improved thermal and pH stability when compared to the free enzymes. The stability of the immobilized protease towards urea was studied both in the presence and absence of calcium chloride

Keywords: stability enhancement, protease, immobilization

Wan Omar Abdullah*, Low Kiat Cheong¹, Vivian Jacob Gomes¹, Sulaiman Osman¹ and Yusof Suboh¹

Department of Medical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor;
¹Department of Parasitology and Medical Entomology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur

(Received 27 October 1997 / Accepted 16 June 1998)

Abstract.
The application of dispersed dye particles as label in immunological assay was investigated as an alternative to enzyme labeled immunoassay (ELISA). Dipsticks prepared from the antibody (Ab) coated nitrocellulose membrane mounted on acetate strips served as capture matrix. Ab absorbed to a commercial brilliant pink colloidal dye particles served as antigen (Ag) detecting reagent. The dipstick developed was compared with plate ELISA for detecting antigenemic cases of Dirofilaria immitis infection in dogs. Evaluation statistics of the dipstick assay varied according to the cutoff value of the ELISA titers. The overall specificity and sensitivity of ELISA was 96.67% and 98.57% respectively. The dipstick performed with a specificity of 85.71 % and a sensitivity of 94.12% when the ELISA titre was 160. There was high level of agreement between these two assay formats ranging from 89.47% to 92.60%. Dipstick assay detected 1% of the occult dirofiliariasis as with the plate ELISA. As the dipstick assay is simpler, rapid, inexpensive, equally sensitive and specific its use in detecting active cases of D. immitis infections in dogs is recommeded especially under field condition. The dipstick immunoassay format would enable veterinary practitioners to quickly diagnose and appropriately treat most cases of the disease.

Keywords: colourimetric, dipstick, inununoassay, dirofilariasis

1. Darah, R. Burke and C. 0. Ibrahim

Fermentation and Enzyme Technology Laboratory, School of Biological Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia

(Received 13 July 1998 / Accepted 27 October 1998)

Abstract.
The lignin peroxidase of Phanerochaete chrysosporium was purified by means of ammonium sulphate precipitation and on an anion exchange chromatography, using a prepacked Mono Q column. The resolution from Mono Q column resulted in 6 different isoenzymes with the recovery of 51 % of which peak 5 (P5) was dominant with 29% recovery. P5 was purified about 23 folds with the specific activity of about 11.7 Umg 1 protein. The molecular weight of P5 was estimated to be 42,000 Dalton by SDS PAGE and the isoelectric point was at pl l 4.2. The optimum temperature and pH were 30 – 37⁰C and 3.0, respectively. The isoenzyme was stable within the pH range of 2-4 and almost 70% of the enzyme activity was retained even after 48 h at 30⁰C.

Keywords: lignin peroxidase, Phanerochaete chrysosporium, solid state fermentation, lignin peroxidase isoenzyme