General Biology

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Browsing General Biology by Author "A. Gashe, Berhanu (PhD)"

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    Aerobic Heterotrophic Bacterial Flora of one of Shalla Hot Springs
    (Addis Ababa,University, 1991-06) Kibret, Mulugeta; A. Gashe, Berhanu (PhD)
    Four sites i n one ot the ho t.. springs ot Shalla were selec ted for the study. The wate r fr om t he sites me rge to form a s t ream whic h forms a te mperature gradient . In this study f our media we r e compa1;' ed tOI? the c ultivation and i solation o f aerobic heter otrophic bac ter i a. The pH of the ho t spring was 8. 7 with a temperature of 9G-56'C . The f o rmulated Illedia were adjusted to pH values o f 7 .0-13 .0. Howeve r , hlgh count s of bacte ria (lxlOl - 7x lOt c f u/ mll was only r egis tered when the pH was ad juste d be twee n 8.0 and 9.0. A medi um containing normal conce ntra tion of Trypton Soya Agar (TSA) was effective i n s uppo rt ing the growth of bacteria t han a med i um c on taining one quarte r strength of TSA o r supplement o f trace minerals. Replaci ng trac e minerals wi th hot s pri ng "" ate r improved the total numbe r of bacteria irowlng and also the number or i so l ates. Thcrmophl1ea were nume r o us (l:d Ol __ 1x l 0' clu/rol) than the rmo tol e r ants (2xlOl_2xl O( c fu/ml) at all sites . The population of Bac illus brevis , Bac illus spbae ricu8, Bacillus s t e arothermQphilu3 and Mi c r ococcus sp. was found to be low at l owe r e nvironmental temperatures than at hliher environmental temperatures . In t he course of t hi s s tudy a total of 44 micro organisms we r e isolated and char.cterlJ1ed. Twenty nine we r e identified to the s pecies level and were touftd to be membe r s o f genus Baci llus . Three isolates were Cram-positive cocci id e ntified t o the ge nus l eve l - Micrococcus. The r e main i ng 12 isolates were ei ther Gram-positi ve , filame ntous or no n- filamentous r od s wh ich need a deta il ed bioc he mi c al analysis for i denlifi c ation . To identify if any o f the isolates may have industrial applications , they we r e c hecked f o r product i on o f amylase and protease . Fifteen o f the isolates produced protease, 18 amylase and eleven I-roduced both amylase and protease.
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    The Effect of Some Physico-chemical Factors on the Production and Activity of Cellulase and B-Glucosidase from Cladosporium SP . BDCC-3
    (Addis Ababa,University, 1990-06) Abraha, Berhanu; A. Gashe, Berhanu (PhD)
    Conditions for the produC"tion, rele8se ... nd ... ctivi. y ot cellulases and B-Glucosidase tro", (11'1"os orium sp. »OCC:-J were investig8 ed. Comparisons !IIade- betwPt"n different carbon !'Iource-s lind their concenTrations for maxi1!lum prorlu~tjon of cellulas8s and aGlucosidase depicted 1 CHC 0.5' Avicel. 1.5'd.-c-I'11ulose. 0.5' filter paper .. nd 0 . 5 cotton to be op timum. From the nitrogen sources used . potassium nitr ate was found to be the nost utilizable by Clados orium 5p. BDCC-J. The OPti~um conce ntrations of nitrate for maximum production of the enzy~p.s were 1'. 1%. 2%. 2% and 1% i n CHC. Avical . -.. -cellulose . filter paper and cotton containing media. r espectively. The most appropri ate de terQent for the release of cellulases and B- Glucosidase was O.J Tween-SO . The enzymes had a wide range of pH . However . t hey were most active at pH 5.0 and 60°C. All enzymes l os t activity when i n cubate~ at 700C for 2 hours. Thus five different optimized media were f ormulated. These were:- 1. Optimized CMe medium 2 (OCI'1-2) containing 1" CHC. 1% KNO) and 0.1% Tween - 80 plus the basal medium 2 . Optimized Av icel medium 2(0 ~M -2) conta ining 0 .5" Avicel. 1% KNOJ and 0.1" Tween - 80 plus the basal medium. J . Optimized .. -Cellulose medium '-(0':' H-2 ) containing 1 . 5% ~ -Cellulose. 2% KNO) and 0.1% Tween - 80 plus the basal medium . 4 . Optimized filter paper medium 2(OFM-2) containinq 0.5% FP . 2 KNO) and 0.1 Tween - 80 plu~ the baSAl medium . 5. Optimized cotton medium 2(OCOH - 2) con t a ining 0.5 cotton. 1% KNOJ and 0.1% Tween - SO plus thp basal medium . The fungus produced maximum level o f CMC - al'le . Avicelase and ~~ -cell usl ese after 6 days o f incubAti on while Fp- asp, co t tonase and .a-Glucosidase were produced J to 6 d~ys later. Cl adosporium sp . BDCC- J produced Cx (cmc-8s e ) much hi.ghpr than CI ( ~v ice'8 s e . ~-'7 - cellulase. FP-ase . cottonase) and R-Glucosidase. A comparative study of free . cytoplasmic and membrane bound enzymes showed that cellulases were extracellular while a-Glucosidase was CytoplAsmic .