Biotechnology

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Browsing Biotechnology by Author "Addis Simachew"

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    Heavy Metal Removal Capability of Bacterial Isolates from Awash Tannery Effluents and Wastewater Sources of Selected Rivers in Addis Ababa
    (Addis Ababa University, 2024-08) Smegnew Melese; Addis Simachew
    Heavy metals from various industrial processes for different purposes pollute soil and groundwater worldwide. They have toxic, mutagenic, andcarcinogenic effects, which pose health risks to the natural biota. Microbe-based biological treatment methods are an environmentally benign and more efficientheavy metal removal technology than conventional ones. The objective of this study was to evaluate the heavy metal removal capability of naturally occurring heavy metal-resistant bacteria both in NAM-SHM and in the actual wastewater, which was collected from ATE and selected tributaries of AARW. Theresult showed that four of the 130 heavy metal-resistance isolates were identified based on their morphological and molecular characteristics. Isolates S. xylosusT14Cd and B. cereusT4Zn were obtained from the Cd and Zn metal-supplemented NAM of the ATE, while S. xylosysW1Cr and S. xylosusW12Pb were obtained from the Cr and Pb of the selected tributaries of AARW. For all those isolates, 30°C and pH 8 were the optimum growth conditions. Isolates S. xylosusW1Cr, S. xylosusT14Cd, S. xylosusW12Pb, and B. cereusT4Zn were shown to have MICs of 3500, 4000, 5000, and 7000 ppm against Cr6+, Cd2+, Pb2+, and Zn2+, respectively. Isolates’ resistance order to a mixture of heavy metals Pb2+, Zn2+, Cr2+, and Cd2+ in 3:3:1:1 (50-800 ppm), respectively, was MCC>S. xylosusT14Cd>S. xylosusW1Cr>S. xylosusW12Pb>B. cereusT4Zn. On the NAM-SHM inoculation, isolates S. xylosusT14Cd, S. xylosusW12Pb, and B. cereusT4Zn gave the maximum removal efficiency for Cd2+ (82.19%), Pb2+ (84.24%), and Zn2+ (80.94%) metals in 8 days, respectively, and Cr6+ (69.9%) was recorded for S. xylosusW1Cr in 6 days of incubation. Whereas, for MCC Cr6+ (79.36%), Cd2+ (88.66%), and Zn2+ (90.22%) in 8 days, and Pb2+ (93.44%) in 6 days, removal efficiency was recorded.The maximum removal efficiency of S. xylosusW1Cr and S. xylosusW12Pb was 83.00 and 79.60% in 6 days, while S. xylosusT14Cd, B. cereusT4Zn, and MCC was 84.88, 76.05, and 87.98% of Cr6+ in 8 days of incubation on the ATE. Moreover, the maximum removal efficiency of S. xylosusW1Cr was 89.75, 98.33, 97.57, and 99.46% of Cr6+, Cd2+, Pb2+, and Zn2+, respectively, on the selected tributaries of AARW in 6 days of incubation. After 6 days of incubation, S. xylosusT14Cd was able to remove the maximum concentration of metals from AARW, with values of89.76, 99.89, and 99.08% of Cr6+, Cd2+, and Pb2+, respectively, and 99.12% of Zn2+ after 8 days. S. xylosusW12Pb was able to remove up to 99.03% ofZn2+ on same medium in 8 days of incubation and also 88.70, 98.93, and 97.77% of Cr6+, Cd2+, and Pb2+, respectively, in 6 days. Similarly, the maximum removal efficiency of B. cereusT4Zn was also 80.48 and 97.25% of Cr6+ and Zn2+, respectively, in 8 days of incubation, while 98.35 and 83.28% of Cd2+ andPb2+, respectively, in 6 days. Whereas, for MCC Cr6+ (90.29%) and Zn2+ (99.99%), in 8 days, while Cd2+ (99.97%) and Pb2+ (99.37%), in 6 days of incubation, removal efficiency was recorded. In conclusion, the four tested isolates are highly efficient for the removal of heavy metals from the NAMSHM and actual wastewater samples. Hence, using these identified and tested bacteria for heavy metal bioremediation is recommended for tannery factory effluents and other industries.
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    Production and Evaluation of the Biotechnological Potential of Alkaliphilic Protease from Tannery Waste Microbes
    (Addis Ababa University, 2025-02-01) Yoseph Sisay; Addis Simachew
    The global leather industry generates significant volumes of tannery waste, contributing to environmental degradation and public health concerns. The study investigated the production of alkaliphilic protease from tannery waste microbes, and its potential applications for detergent and leather industries were also evaluated. After the isolation of more than 100 bacterial strains and screening of 22 alkaline protease-producing bacteria, strain YATW18 has been identified as the most efficient producer of extracellular alkaline protease with 92.65 U/ml enzyme activity in 48 hours. Molecular characterization has assured the genus and species name of strain YATW18to be Alkalihalophilus pseudofirmus. The partial sequence of Alkalihalophilus pseudofirmus strain YATW18 16S rRNA gene was submitted to the NCBI database and the accession number was obtained as PP942174. Fructose as a carbon source exhibited the highest enzyme activity with an average yield of 82 2.98 U/ml, and peptone as a nitrogen source resulted in the highest enzyme activity of 96.86 2.98 U/ml. From locally available substrates, water hyacinth has demonstrated the highest alkaline protease yield of 661.85 10.98 U/g. The mean differences in optimizing parameters including carbon sources, nitrogen sources, and locally available substrates were statistically significant at P 0.05. Physicochemical characterization of alkaline protease showed optimum activity at 55 and pH 10. The enzyme reached its saturation level within 20 minutes of incubation time and then linear activity was observed until 45 minutes. Alkaliphilic protease (77.92 U/ml and 99.6 U/ml) showed high protein (egg yolk) stain removal efficiency and dehairing (goat and sheep skins) capacity