ABSTRACT

Dairy wastewater is increasingly becoming an environmental concern. There is a widespread interest

in the use of beta-galactosidase (EC 3.2.1.23) to hydrolyze lactose in milk and dairy products which

aid in improving their functional and digestive properties. An attempt was made to isolate fungi from

dairy effluent using standard culture techniques. Physicochemical characteristics and proximate

composition of the dairy effluent was analyzed. The fungi isolated were subsequently screened using

Ortho-nitrophenol-beta-D-galactopyranoside (ONPG) discs method for potential to produce beta-

galactosidase. The isolate showing beta-galactosidase activity was selected and used to produce

beta-galactosidase under submerged fermentation using the dairy effluent as a substrate. A total of

nine (9) fungi were isolated from the dairy effluent belonging to the Genera Aspergillus, Rhizopus,

Rhizomucor and Penicillium with Aspergillus having the highest frequency of occurrence (67%).

Physicochemical analyses of the raw dairy effluent revealed the effluent had a pH of 6.8 (±0.20),

electrical conductivity of 645µs/cm (±1.00) and total dissolved solids of 324mg/L (±2.00). The

dissolved oxygen and biochemical oxygen demand were 200mg/L (±1.00) and 100mg/L (±1.70)

respectively while the nitrates, phosphates and sulfates were 1.4x10-3% (±1.0x 10-4), 54.94mg/L

(±0.79) and 13.66mg/L (±0.61) respectively. The proximate composition of the dairy effluent

revealed ash, lipid, protein and carbohydrate contents were 0.15% (±0.01), 5.85% (±0.02), 0.88%

(±0.01) and 13.13% (±0.00) respectively. Only Rhizopus species showed beta-galactosidase activity

and was used to produce extracellular beta-galactosidase. A maximum beta-galactosidase activity of

4.65U/mL (±0.02) was obtained with the selected Rhizopus species. It was concluded that Rhizopus

species could be a potential fungal strain for beta-galactosidase production using the dairy effluent as

substrate.

 CHAPTER ONE

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