Muhammad Sohail - Profile on Academia.edu (original) (raw)

Papers by Muhammad Sohail

Bacteria associated with rhizosphere are recognized as highly diverse bio control agents. Product... more Bacteria associated with rhizosphere are recognized as highly diverse bio control agents. Production of antagonistic substances by such bacteria has significance in the control of phytopathogenic microorganisms. Pseudomonas aeruginosa SA 188, an indigenous isolate from rhizosphere was found to produce a high molecular weight pyocin which was resistant to proteolytic enzymes (protease, proteinase K, pepsin, papain and lipase). This pyocin exhibited antibacterial activity against both the Gram-positive and Gram-negative bacterial strains including Corynebacterium xerosis, Listeria monocytogenes, Micrococcus luteus, Staphylococcus aureus, Streptococcus pyogenes and Escherichia coli. The production of this pyocin by P. aeruginosa SA 188 started in the early logarithmic phase of the growth cycle and reached maximum at the late log phase. A single peak of protein was demonstrated by size exclusion chromatography (using Sephadex G-75 column). There was an increase in the specific activity after each step of purification and the final purification of pyocin SA 188 was found to be 4.6 folds. Electrophorogram of this protein revealed a single band of molecular mass approximately 45 kDa by SDS-PAGE (10% acrylamide denaturing gel). The band was found bioactive in the direct gel overlay.

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.

Cellulases are a group of hydrolytic enzymes capable of hydrolyzing the most abundant organic pol... more Cellulases are a group of hydrolytic enzymes capable of hydrolyzing the most abundant organic polymer i.e. cellulose to smaller sugar components including glucose subunits. Cellulases have enormous potential in industries and are used in food, beverages, textile, laundry, paper and pulp industries etc. This study was aimed to screen the cellulytic ability of fungi from native environmental source. Furthermore, optimal condition for enzyme activity and induction of enzyme synthesis were also determined.

Starches are one of the most important naturally occurring glucose polymers that are present in p... more Starches are one of the most important naturally occurring glucose polymers that are present in plants. They are used as the starting material for the production of a variety of different types of compounds of commercial importance. The usual process is the treatment of starch at an elevated temperature to gelatinize followed by liquefaction by chemicals or by enzymes. Enzymatic liquefaction has an edge over chemical treatment process. Microbes are, in general, the source of commercial enzymes. Present study was initiated to screen the microbial population for their ability to possess amylolytic potential where 117 strains of bacteria and 130 fungal strains were isolated and screened. A considerable number of both were found to produce amylase. Bacillus sp., and Aspergillus sp., were the most active amylase producers. Bacterial enzymes showed maximum activity at slightly elevated temperature and at alkaline pH while one of the fungal enzymes retained most of its activity even at a temperature of 80ºC, however, level of activity was reduced when reaction was carried out at alkaline pH. Genetic studies revealed that starch is a suitable inducer in case of fungi, while maltose seems to be a better inducer than that of starch in case of bacteria.

One hundred and twenty eight fungi isolated from the native environments, including soil, plant, ... more One hundred and twenty eight fungi isolated from the native environments, including soil, plant, deteriorating distempered-wall and spoiled orange-juice samples and 32 isolates obtained from the culture collections were screened for hydrolytic enzyme production. A large proportion (71.25%) of fungal strains belonged to the genus Aspergillus followed by genera Alternaria, and Rhizopus. These strains were sorted on the basis of their hydrolytic potential of starch, cellulose, protein, xylan and pectin. Some selected strains that produce high levels of enzymes, grown in shake-flask and amylase, cellulase, protease, xylanase and pectinase were quantitatively evaluated. Members of the genus Aspergillus appeared to exhibit the greatest diversity in terms of high levels of all the investigated hydrolases.

Cellulase production was studied after cultivation of Alternaria sp. MS28 in cellulose containing... more Cellulase production was studied after cultivation of Alternaria sp. MS28 in cellulose containing media. This fungus produces different component activities of cellulases, a property influenced by growth temperature. The data indicates that the production of cellulases is a genetically regulated process in the Alternaria sp. MS28, where endoglucanase production was triggered in the presence of CMC; β-glucosidase production by salicin; however, the presence of glucose suppressed the cellulase production. The growth and cellulase production kinetics revealed that the production of endoglucanase and βglucosidase started in early log-phase and attained its peak in stationary phase. The higher rates of biomass production and shorter generation time were noted in SDB. The rate of endoglucanase and β-glucosidase production was higher in CMC and salicin containing medium, respectively. Partial characterization of cellulases in cell-free culture supernatant showed that endoglucanase has its optimum activity at 50 o C and pH 6.0; while β-glucosidase at 45 o C and pH 4.5. The melting temperature for endoglucanase and β-glucosidase were 57 o and 59 o C, respectively. Activity of both the enzymes was slightly affected by the presence of EDTA indicating that these enzymes may not require divalent metallic ions for their activity.

The aim of this study was to investigate the production of bacteriocin/bacteriocin-like inhibitor... more The aim of this study was to investigate the production of bacteriocin/bacteriocin-like inhibitory substances (BLIS) from Bacillus subtilis BS15, isolated from soil. The inhibitory substance was partially purified and characterized as BLIS with a molecular-weight of 3-5 kDa, as determined by SDS-PAGE. Its production was observed during the late exponentialphase or at the beginning of stationary-phase. It retained its activity up to 80°C and over a wide range of pH i.e., 3-9. It was found active against several clinically important bacterial species such as Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Salmonella typhi and also against the food-spoilage causing microbes, and may be considered as future food preservative.

Soil-borne microorganisms are widely used as inoculants to improve crop yield. However, bacteria ... more Soil-borne microorganisms are widely used as inoculants to improve crop yield. However, bacteria from other sources have scarcely been reported for their plant growth promoting abilities. This study was aimed to assess plant growth promotion abilities of bacteria from different sources including clinical samples, air and soil. The study was commenced with the isolation of more than two hundred and thirty bacteria and screening for the ability to solubilize mineral phosphates. It was observed that a large proportion of bacteria isolated from garden soil can exert phosphate solubilizing activity. Whereas, strains isolated from clinical samples and air showed decreased P solubilization. The phosphate solubilizing bacterial isolates were also studied for their ability to promote plant growth. The ability to increase plant root and shoot length was mainly observed by the strains of Rhizobium and Bacillus subtilis. The strains were screened for their bacteriocinogenic potential and it was found that none of the strains can produce bacteriocin-like-inhibitory substances (BLIS). Studies on root colonization to mungbean and chickpea plants by the strains of Rhizobium and B. subtilis revealed that strains can bind root tightly with a higher bacterial density and hence can be used as prospective biofertilizer.

Fungal cellulases are well-studied enzymes and are used in various industrial processes. Much of ... more Fungal cellulases are well-studied enzymes and are used in various industrial processes. Much of the knowledge of enzymatic depolymerization of cellulosic material has come from Trichoderma cellulase system. Species of Trichoderma can produce substantial amounts of endoglucanase and exoglucanase but very low levels of b-glucosidase. This deficiency necessitates screening of fungi for cellulytic potential. A number of indigenously isolated fungi were screened for cellulytic potential. In the present study, the kinetics of cellulase production from an indigenous strain of Aspergillus niger MS82 is reported. Product formation parameters of endoglucanase and b-glucosidase (Q p + Y p/s ) indicate that A. niger MS82 is capable of producing moderate to high levels of both endoglucanase and b-glucosidase when grown on different carbon containing natural substrates, for example, grass, corncob, bagasse along side purified celluloses. Furthermore, it was observed that the production of endoglucanase reaches its maximum during exponential phase of growth, while b-glucosidase during the Stationary phase. Enzyme production by solid-state fermentation was also investigated and found to be promising. Highest production of cellulase was noted at pH 4.0 at 35 8C under submerged conditions. Growth and enzyme production was affected by variations in temperature and pH.

A mutant MS301 of Aspergillus niger MS82 showed 1.5 to 2.5-fold improved endoglucanase and β-gluc... more A mutant MS301 of Aspergillus niger MS82 showed 1.5 to 2.5-fold improved endoglucanase and β-glucosidase activity when grown on crude lignocellulosic substrates under solid-state and submerged conditions. Indicators of thermal stability of enzymes (T m and T 1/2 ) showed that the wild type and mutant endoglucanase was more heat-resistant compared to βglucosidase. However, mutant and parent enzymes shared almost the same values for melting temperatures and half-lives. Endoglucanase and β-glucosidase from both the strains showed optimum activity under acidic pH. Energy of activation (Ea) of mutant β-glucosidase was substantially lower than the parent enzyme while E a of mutant endoglucanase was slightly less than the parent. The lowered E a values can be attributed to the improved β-glucosidase activity of the mutant strain. Moreover, the MS301 enzymes were better in hydrolyzing purified and crude cellulosic materials than the parent MS82.

Apple (Malusdomesticaborkh) is one of the popular fruit with an annual global production of sever... more Apple (Malusdomesticaborkh) is one of the popular fruit with an annual global production of several million tones. The use of apple in food production industry led to the generation of huge waste materials in the form of peels and pomace. Owing to the high amounts of lignocellulosics present in the wastes, these can be served as substrate for the production of plant cell-wall degrading enzymes (CWDE). The present study describes the potential of an indigenously isolated strain of Aspergillusfumigatusto produce plant CWDE using apple peels under submerged as well solid-state fermentation. It was observed that the strain was able to produce higher activity of pectinase and xylanase under both the types of fermentation at 30 o as well as at 40 o C. While less titers of filter paperase, endoglucanase, -glucosidase was obtained. However, the production of plant CWDE was influenced when the apple peels were supplemented with carboxymethyl cellulose, xylan, pectin and lactose. Interestingly, a structurally irrelevant substrate, lactose, acted as inducer, particularly for the production of pectinase.

The use of microorganisms for starch degradation in various processes has not only eliminated the... more The use of microorganisms for starch degradation in various processes has not only eliminated the need to use various chemicals, but has also reduced the expenditure on these processes. In modern biotechnology, yeasts have gained sufficient importance due to several reasons; the most important being their harmless status for human consumption. The need to search for some good amylolytic yeast species, is therefore, the need of time, since such strains may not only be used for the bulk production of commercial products like bioethanol, but also to obtain amylases in larger amounts, which may then be used wherever required. The present review focuses on the various amylolytic yeast species and their potential industrial applications along with a brief discussion about amylases.