ABSTRACT
Aims: Palm oil mill effluent (POME) erodes the principal biophysical characteristic of both soil and water when discharged untreated but could be exploited as medium for microalgae cultivation due to its vast mineral contents. Place and Duration of study: POME samples were collected from a local palm oil processing mill at Nsukka, Enugu State, Nigeria. A part of the study was done at the Graduate School of Life and Environmental Sciences, University of Tsukuba, Japan while the rest at the University of Nigeria, Nsukka between March and September, 2012. Methodology: Chlorella sorokiniana C212 was grown in several Batches (A-D) of POME supplemented with urea (60 mg/L) before subjecting to different sterilization protocols. Cultivation was conducted in shaker flasks at 150 rpm, 1 vvm, 3000 lux and pH 7.0±0.2. Results: The filter sterilized Batch (B) promoted the highest (1070±30 mg/L) dry cell weight (DCW), lipid (156±12 mg/g-cell) and chlorophyll (1.59±0.11 mg/g-cell) contents while chemical oxygen demand (COD) decreased by 45±08%. The autoclaved medium (Batch A) gave the least DCW (310±20 mg/L), lipid production (40±05 mg/g-cell) and chlorophyll content (0.58±0.02 mg/g-cell) while COD reduced by 20±04%. The highest COD decrease (70±05%) was achieved in the unsterilized Batch (D). Batch B was most positively affected by dilution because at 75% concentration, DCW increased to 1360±30 mg/L, lipid contents to 174±10 mg/g-cell, chlorophyll to 1.87±0.14 mg/g-cell the while COD declined by 63±03%. Conclusions: POME has potential for use in microalgae cultivation with significant saving in treatment costs.
ABSTRACT
Aims: To produce a robust starch hydrolyzing enzyme (improved catalytic and noncatalytic properties) by the adsorption of the soluble enzyme on micro bead silica gel. Place and Duration of Study: Department of Life Sciences and Bioengineering, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba-shi Ibaraki-ken, Japan between July 2009 and August 2010. Methodology: Ten types of Micro Bead silica gel with pore sizes ranging from 0.4-100 nm were screened to determine the best support for the immobilization of a microbial raw starch digesting amylase (RSDA). The micro bead which gave the highest yield was selected for further studies. Properties of the immobilized enzyme were compared to the free type to determine the effect of immobilization on catalytic, storage and operational stability. Results: Micro Bead 300 A gave the highest yield and the optimum condition for adsorption of the RSDA was at pH 5, 25°C for 24 h. Optimum pH of the immobilized enzyme shifted from 5 to 4.5 and optimum temperature from 30 to 50°C. The immobilized amylase retained over 70% of its initial activity after 12 h incubation at 70°C in 0.2 M citrate phosphate buffer pH 5 whereas free enzyme lost 92% initial activity under same conditions. Immobilized enzyme retained 95% activity after 10 batch reactions of 30 min each and 100% activity after storage for 6 weeks at room temperature. Conclusion: Immobilized RSDA was marginally more pH and temperature stable compared to the native type. It also exhibited storage stability and could be re-used repeatedly without considerable desorption during washing. The kinetic and stability features combined with the properties of the support make this process appealing for industrial application.