ABSTRACT
The study analyzed quantitatively and qualitatively the biogas produced from cowdung by indigenous microbial consortia. Four 20L bioreactors were used for the study. The bioreactors were constructed to imitate the fixed batch prototype. The study lasted for six months and it was carried out at the Microbiology Laboratory of Anambra State University, Anambra State, Nigeria. Slurry was prepared in bioreactors. The substrates in the bioreactors were water and manure (WM), rumen fluid and manure (RM-1 and RM-2), medium and manure (MM). The pH, the total solids (TS), volatile solids (VS) and total volatile fatty acid (VFA) characteristics of the substrate before and after digestion were determined using standard method. Quantification and qualitative analysis of biogas production was by liquid displacement and gas chromatography methods respectively. The microbial analysis of the substrate was carried out using spread plate method. The results of the TS, VS and VFA were 400 mg/l, 92mg/l and 16.7 mg/l respectively in the predigested samples and 92 mg/l, 17.4mg/l and 28.3mg/l respectively in the post digested samples. The quantity of biogas produced at fourth month was 60 ml, 128ml and 220ml from WM, MM and RM-1 respectively. The qualitative analysis showed that the prominent biogas produced was methane. The cultural morphology revealed Gram positive rods with creamy irregular edges. The average heterotrophic counts at the end of each month for a period of four months were 18.5x105cfu/ml, 21.1 x105cfu/ml and 26.7x105cfu/ml for WM, MM and RM respectively. The results of the research concluded that high quantity of biogas can be produced using cow dung. Approaches and technology for more efficient biogas producing consortia are proposed.
ABSTRACT
Four brands of yogurt sold by street vendors in Onitsha Metropolis, Anambra State, Eastern Nigeriia were sampled, the pH was determined and microbiological assessments were conducted in order to ascertain the total heterotrophic bacteria, coliforms and yeast in the samples (A – D) during a seven day period. The results revealed that values of pH monitored varied from 3.69 – 4.50 while a total of five bacteria species belonging to Escherichia coli, Staphylococcus aureus, Streptococcus, Lactobacillus and Bacillus species, and three fungi species belonging to Aspergillus, Rhizopus and Saccharomyces were isolated from the samples. Sample B had the highest mean heterotrophic bacteria count with a value of 6.1 x 105 cfu/ml. Statistical analysis of heterotrophic bacteria count among the 4 sample groups had p-value =0.0000374. There is a significant difference in the heterotrophic bacteria count among the groups. Low titre values of starter cultures were recorded in the control samples. Escherichia coli, an indicator of coliform was detected in all the samples and the value of 4.4 x 105 cfu/ml was observed in sample B. Coliforms, S. aureus, Bacillus species and fungi were not detected from control samples purchased directly from the producing companies. Statistical analysis of coliform count in the four groups had p-value=0.529296. There was no significant difference in the coliform count among the 4 sample groups at α =0.05 and p-value =0.529296. The findings suggest that the yogurt traded by street vendors in Onitsha Metropolis has poor microbiological quality control. This poses danger to public health. Therefore, attention of the appropriate government agencies and manufacturers is needed to ensure that sale of yogurt by vendors is done in most appropriate condition and in a mobile refrigerator to maintain adequate temperature, thereby, reduce contamination.