Abstract
Amylases (EC 3.2.1.1) are cellwall degrading enzymes associated with the pathogenicity of microorganisms in the spoilage of tomato fruits. The use of amylase in many industries has made it very important to optimize production process to achieve maximum yields. Screening and partial purification of Amylase from Aspergillus niger isolated from tomato (Lycopersicon esculentum Mill.) fruits was studied. Amylase producing fungi were isolated from fresh tomatoes kept at ambient temperature (28±1˚C). Isolates were characterized on the basis of their morphological and cultural techniques. Partial purification of amylase was carried out by ammonium sulphate precipitation. The enzyme activity was determined and optimum conditions were obtained. The molecular weights of the crude and partially purified Amylase were determined by SDS PAGE method. A total of five isolates were obtained using basic screening technique for amylase activity, one of the isolates (Isolate code F2) exhibited maximum amylase activity. The fungi isolate code F2 was identified as Aspergillus niger. Optimum conditions for Amylase AMY F2 were ascertained at pH 6.0; temperature 30°C; substrate concentration of 0.3mg/ml, and time of heating of less than 10min. The molecular weights of the crude and partially purified Amylase AMY F2 were found to be 55kDa and 35kDa respectively by SDS PAGE method. Microorganisms had been an encouraging means of economical production of enzymes in large scale for the food and drug industry.
Highlights
Tomato (Lycopersicon esculentum Mill.) has fleshy endocarp which belongs to the berry class [1]
Enumeration of Fungal Population The total fungal spore count for the tomato fruits stored in the post-harvest storage system was within the range of 1.0 x 105 – 4.0 x 106spores/ml while those fruits stored in the refrigerator had fungal spore count range of 1.0 x 105 – 3.0 x 106spores/ml and fungal spore count of 2.0 x 102 – 4.0 x 1011spores/ml for the fruits stored at ambient temperature (Table 1)
The result of this research had the total fungal population ranges between 1.0 x 105 and 4.0 x 106spores/ml for the tomato fruits stored in the postharvest storage system, those in the Refrigerator ranges between 1.0 x 105 and 3.0 x 106spores/ml while the tomato fruits stored at ambient temperatures had fungal population range of 2.0 x 102 and 4.0 x 1011spores/ml
Summary
Tomato (Lycopersicon esculentum Mill.) has fleshy endocarp which belongs to the berry class [1]. The plant cell wall which is a protective layer that coats the outer surface usually plays many roles, including controlling movement of water into the fruit [7] It filters potentially damaging UV light, and limits attack by pathogens [5]. There is need for constant research to isolate the fungi associated with tomato fruits deterioration with the view to providing suitable solutions of preserving the tomato fruits, keeping them fresh up to when they reach the consumers [12] This helps to ensure all year round availability and to protect the public health [13].Contamination of fresh tomatoes by microorganisms occurs naturally because the fruits are exposed to the environments during harvest, transportation and storage [7]. Refrigerator temperature arrests the growth of microorganisms while those that could survive extremely low temperatures still grow when the cell walls are broken due to the fact that released fluids serve as nutrients for the microorganisms [8,18]
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