Muhammad Sohail | University of Karachi (original) (raw)

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Pseudomonas aeruginosa, in spite of being a ubiquitous organism (as it is found in soil, water, a... more Pseudomonas aeruginosa, in spite of being a ubiquitous organism (as it is found in soil, water, and humans), is also an opportunistic pathogen. In order to maintain its diversity in the community, it produces various toxic proteins, known as, bacteriocins. In the present study, pyocin SA189, which is a bacteriocin produced by P. aeruginosa SA189 (isolated from a clinical sample) was characterized. P. aeruginosa SA189, as identified by the conventional and 16S rRNA gene amplification, produced pyocin SA189 of molecular weight of 66 k Da. The pyocin showed antimicrobial activity against several clinically relevant Gram-positive and Gram-negative bacteria and was substantially stable for wide ranges of temperature and pH. Furthermore, the pyocin also retained its biological activity upon treatment with metal ions, organic solvents, and various proteolytic and lipolytic enzymes. The data from the growth kinetics indicated that the maximum bacteriocin production occurred in the late log phase. Overall, our results signify the potential of pyocin SA189 as a bio-control agent.

Amylases are omnipresent and exceedingly demanded industrial enzymes. In this study, the conditio... more Amylases are omnipresent and exceedingly demanded industrial enzymes. In this study, the conditions of extracellular amylase production from a fungal strain A. tubingensis SY1 were statistically optimized by applying Plackett-Burman equation, under submerged fermentation conditions. Maximum enzyme activity was noted in a medium containing (g/L); Starch (5.0), Peptone (10.0), KH 2 PO 4 (2.0), NH 4 NO 3 (3.0), KCl (1.0), MgSO 4 .7H 2 O (1.0), FeSO 4 .7H 2 O (0.01), Agitation (200 rpm) with an inoculum size 1%. As witnessed from Pareto chart; variables that were most important for amylase production were Peptone, agitation; MgSO 4 .7H 2 O followed by inoculum size. Partial characterization of the crude enzyme revealed that the optimum temperature and pH for enzyme activity was 60 o C and 5.6, respectively. The residual activity of the enzyme was reduced to 50% after storage for ~3h at 44°-64°C. The enzyme was, however, stable at a pH range of 3.6-5.6 for up to 3h.

Aspergillus terreus MS105 was originally isolated from soil and screened for cellulase production... more Aspergillus terreus MS105 was originally isolated from soil and screened for cellulase production in the presence of various carbon sources including car-boxymethyl cellulose (CMC), avicel, sigmacell, filter-paper and salicin. CMC induced the production of endoglucanase (EG) and filter-paperase while the levels of b-glucosidase (BGL) were increased when salicin was present in the medium. Nature of production medium influenced the duration of lag-and log-phase of the growth, rate of fungal dry-mass and enzyme production. The vol-umetric and specific productivity of cellulase under submerged fermentation of grass were 1.7–20-folds higher than sugarcane-bagasse, corncob and commercially available purified substrates. Nonetheless, solid state fermentation (SSF) of crude substrates also yielded high volumetric productivity of EG and BGL. The studies on characterization of enzymes showed that EG was more ther-mostable than BGL with an optimum activity at 70 °C and a melting temperature of 76 °C. A 1.2–1.5-folds increase in EG activity was observed in the presence of K ? , Ca 2? and Mg 2? , whereas, the EG and BGL activities remained unaffected in the presence of EDTA. Both the enzyme activities performed optimally under acidic range of pH.

Xylanolytic and cellulolytic potential of a soil isolate, Aspergillus fumigatus (MS16) was studie... more Xylanolytic and cellulolytic potential of a soil isolate, Aspergillus fumigatus (MS16) was studied by growing it on a variety of lignocellulosics, purified cellulose and xylan supplemented media. It was noted that carboxymethyl cellulose, salicin and xylan induce the production of endoglucanase, β-glucosidase and xylanase, respectively. The study revealed that Aspergillus fumigatus (MS16) co-secretes xylanase and cellulase in the presence of xylan; the ratio of the two enzymes was influenced by the initial pH of the medium. The maximum titers of xylanase and cellulase were noted at initial pH of 5.0. Relatively higher titers of both the enzymes were obtained when the fungus was cultivated at 35 o C. Whereas, cellulase production was not detected when the fungus was cultivated at 40 o C. The volumetric productivity (Q p) of xylanase was much higher than cellulases. The organism produced 2-3 folds higher titers of xylanase when grown on lignocellulosic materials in submerged cultivation than under solid-state cultivation, suggesting a different pattern of enzyme production in presence and in absence of free water. The partial characterization of enzymes showed that xylanase from this organism has higher melting temperature than endoglucanase and β-glucosidase. The optimum temperature for activity was higher for xylanases than cellulases, whereas the optimum pH differed slightly i.e. in the range of 4.0-5.0. Enzyme preparation from this organism was loaded on some crude substrates and it showed that the enzyme preparation can be used to hydrolyze a variety of vegetable and agricultural waste materials.

Three strains of Aspergillus niger were retrieved from culture collection of the Department of Mi... more Three strains of Aspergillus niger were retrieved from culture collection of the Department of Microbiology, University
of Karachi, Karachi, Pakistan and were studied for their ability to produce cellulases. Cultivation at different temperatures
and in presence of various carbon sources revealed that all the three strains produced more amounts of endoglucanase, β-
glucosidase and filter-paperase activities at 35o
C; carboxymethyl cellulose promotes the production of filter paperase and
endoglucanase activities whereas salicin induced β-glucosidase activity. Experiments on growth and enzyme production
kinetics showed that generation time and hence volumetric rate of biomass production is influenced by the carbon source
used in the medium; simple carbon source, such as glucose favored the growth of all the strains. Cellulases from all the
strains showed optimum activity at temperature >50o
C and under acidic range of pH, while melting temperature was 64-
65o
C. These findings affirm that cellulases from A. niger are potential candidates as alternative to Trichoderma cellulases.

Filamentous fungi are considered to be the most important group of microorganisms for the product... more Filamentous fungi are considered to be the most important group of microorganisms for the production
of plant cell wall degrading enzymes (CWDE), in solid state fermentations. In this study, two
fungal strains Aspergillus niger MS23 and Aspergillus terreus MS105 were screened for plant
CWDE such as amylase, pectinase, xylanase and cellulases (-glucosidase, endoglucanase and
filterpaperase) using a novel substrate, Banana Peels (BP) for SSF process. This is the first study, to
the best of our knowledge, to use BP as SSF substrate for plant CWDE production by co-culture of
fungal strains. The titers of pectinase were significantly improved in co-culture compared to
mono-culture. Furthermore, the enzyme preparations obtained from monoculture and co-culture
were used to study the hydrolysis of BP along with some crude and purified substrates. It was observed
that the enzymatic hydrolysis of different crude and purified substrates accomplished after 26
h of incubation, where pectin was maximally hydrolyzed by the enzyme preparations of mono and
co-culture. Along with purified substrates, crude materials were also proved to be efficiently degraded
by the cocktail of the CWDE. These results demonstrated that banana peels may be a potential
substrate in solid-state fermentation for the production of plant cell wall degrading enzymes to be
used for improving various biotechnological and industrial processes.