The aim of this work is to determine the effect of temperature on the population of hydrocarbon degrading bacteria in palm oil mill effluent. This was done at the Department of Microbiology, University of Abuja, Abuja, F.C.T Abuja, Nigeria, between June 2015 and August 2015. Samples of POME were inoculated with Pseudomonas aeruginosa, Bacillus subtilis, Klebsiella and Staphylococcus aureus. Microbial growth was measured by determining the total viable counts in the medium containing POME and control. The isolates were analyzed for the population of bacteria at temperatures 40C, 350C and 400C with incubation periods after 24 hours, 7days and 14days. Analysis of variance of POME isolates shows that there is no significant difference between the time of incubation and temperature since P- Value (0.159) > α (0.05) for time and P- Value (0.145) > α (0.05) for temperature. ANOVA for control isolates shows that there is significant difference between incubation period of 24 hours, 7days and 14days since p- Value < α (0.05). The highest bacteria population was recorded after the 7th day of incubation at 350C from Pseudomonas aeruginosa 1.66 x 108 ± 0.6 to Klebsiella 1.27 x 108 ± 0.6.
Palm oil is one of the most important vegetable oil in the world’s oil fat market. The extraction and purification processes generate different kinds of wastes generally known as palm oil mill effluent (POME).
The biodegradation of hydrocarbons by microorganisms has become the main mechanism for eliminating palm oil and petroleum derived pollution in the environment. Palm oil mill effluent is waste water generated from palm oil milling activities which requires effective treatment before discharge into water course because of its highly polluting properties (Phaik et al., 2010). The raw effluents contain 90% – 95% water and include residual oil, soil particles and suspended solids (Phaik et al., 2010).
The techniques of biological control over hydrocarbon based pollutants is a promising new technology, thanks to its low cost and absence of secondary contamination (Vasudevan and Rajaram, 2001; Agnieszka and Zofia, 2010). In the course of biological restoration of contaminated soil the main factors that affect the effect of remediation include pH value, the nutritional level, the hydrocarbon degrading bacteria and the temperature, among which the impact of hydrocarbon degrading bacteria on the remediation effect is critical (Venosa and Zhu, 2003; Chaillan et al., 2006). Under certain extreme environments such as in the high temperature and extreme arid regions, it is very important to select the locally specific and extremely indigenous microorganisms capable of degrading hydrocarbons.
Oil palm Elaeis guineensis cultivation and processing like other agricultural and industrial activities, also raise environmental issues. Palm oil processing is carried out using large quantities of water in mills where oil is extracted from the palm fruits. During the extraction process, about 50% of the water results in palm oil mill effluent. It is estimated that for every 1 tonne of crude palm oil produced 5 -7.5tonnes of water end up as palm oil mill effluent (POME) (Okwute and Isu, 2007; Wu et al., 2009).
In Nigeria’s palm oil industry, most of the palm oil mill effluent produced by small scale traditional operators undergo little or no treatment and are usually discharged in the surrounding environment. This could pollute streams, rivers or surrounding land (Okwute and Isu, 2007). River water consequently turns brown, smelly and slimy. Often, fish and other aquatic organisms get killed and locale people are denied of the availability of local water sources for domestic uses and fishing (Ezemonye et al., 2008).
The effect of crude oil pollution on the properties of soil has been the subject of many studies. Okolo et al., (2005) reported that oil pollution increase carbon and reduce soil nitrates and phosphorus. Similarly, Adedokun and Ataga, (2007) reported that any contact of soil with crude oil results in damage to the soil microorganisms and plants while Onuah et al., (2003) among others have shown that crude oil pollution prevents oxygen exchange between soil and the atmosphere due to hydrophobic properties of oil.
Palm oil mill effluent has been an area of interest to researchers in the field of environmental microbiology, and biotechnology. Most especially, because of the impact it has on the environment (soil and water). Among the various conditions necessary for the degradation of POME by hydrocarbon degrading bacteria, I am interested in knowing about the effect of temperature on hydrocarbon degrading bacteria, how it affects growth rate and population of bacteria, as a means of contributing to the many work that has been done.
1.3 Aim and objectives
The reason for this work is to determine the effect of temperature on the population of hydrocarbon degrading bacteria in palm oil mill effluent.
The specific objectives are:
I. Sterilization of all media and materials.
II. Inoculation of POME and the control with bacteria isolates.
III. Incubation of inoculated POME and control isolate at temperatures 40C, 350C and 400C, for 24 hours, 7 days and 14 days.
- Determination of total viable counts through serial dilution and spread plate techniques.