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Studies on Cellulases and Xylanases of Indigenous Yeast Strains

Thesis Info

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Author

Shariq, Maria

Program

PhD

Institute

University of Karachi

City

Karachi

Province

Sindh

Country

Pakistan

Thesis Completing Year

2018

Thesis Completion Status

Completed

Subject

Microbiology

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/11967/1/Maria%20Shariq_Microbio_2018_UoK_HS%20Diff.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727281889

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Lignocellulose (LC), a composite of cellulose, hemicellulose and lignin is considered as naturally occurring chemical feedstock. Pakistan being an agricultural country, generates huge amounts of LC substrates in the form of agricultural waste. Global demand for chemicals and insufficient supply of energy in Pakistan, necessitates comprehensive studies on the utilization of LC substrates. LC materials can be used as substrate for the production of plant cell wall degrading enzymes (PCWDEs) including industrially important enzymes, cellulase and xylanase. At present, bacteria and filamentous fungi are employed for the production of cellulases and xylanase on large scale, whereas, very few yeasts have been studied in this regard. Keeping in view the importance of yeast cellulase and xylanase, the present study was conducted on isolation, production and characterization and possible biotechnological application of indigenous yeast strains. The study was initiated with the isolation of yeast strains from environmental samples and retrieval from culture collection available at the Department of Microbiology, University of Karachi. Total 225 yeast strains were subjected to qualitative screening, as well as, quantitative screening for cellulase and xylanase. On the basis of titers of the enzymes, three yeast strains were selected for further studies, MK-157 and MK-160, for endoglucanase (EG) and Xylanase (Xyl) production, repectively, while MK-118 for EG, β-glucosidase (BGL) and Xyl production. The strain, MK-157, was identified on morphological and biochemical basis as Saccharomyces cerevisiae, and was confirmed on molecular basis using ITS primer and species specific primers. Production of EG from S. cerevisiae MK-157 was optimized through shake flask method by adopting one factor at a time (OFAT) strategy. Maximum production of EG from MK-157 was obtained at 30 °C with media pH 7.0 and 1% CMC. EG from MK-157 was characterized and the data revealed that enzyme optimally active at 30 °C under acidic pH in the presence of 1% CMC. The gene encoding EG was isolated, sequenced and submitted to Genbank with accession number MF871644 and KY660547. The strain, MK-160, was identified on morphological, cultural and biochemical basis as Candida tropicalis. The optimized conditions for Xyl production from MK-160 were temperature, 40 °C; pH, 7; and substrate concentration, 0.5%. Optimal activity of Xyl from MK-160 was observed at 40 °C under acidic condition and with 2% of beechwood xylan. Likewise, the strain, MK-118, was identified as C. tropicalison on the basis of morphological, cultural and biochemical tests. MK-118 was studied for coproduction of EG, BGL and Xyl. Production of all the three enzymes from C. tropicalis MK-118 was optimized, separately. Production parameters varied greatly for individual enzyme. Such as for EG and BGL production, cultivation at 40 °C under neutral conditions was maximum while 25 °C with acidic condition was considered as suitable for Xyl production. The highest titers of EG, BGL and Xyl from MK-118 were obtained in presence of 0.5% of CMC, 1.5% of salicin and 1% of xylan, respectively. Moreover, the parameters affect differently when enzyme preparations were characterized. The maximum activity of the EG and BGL was noted at 30 °C while Xyl worked optimally at 40 °C. BGL and Xyl from MK-118 showed maximum active with 1.5% salicin and xylan, respectively, while EG exhibited highest activity with 2% of CMC. Selected yeast strains and their enzymes were also studied for their possible biotechnological application. S. cerevisiae MK-157, C. tropicalis MK-118 and MK-160 were cultivated under submerged fermentation (SmF) of sugarcane bagasse (SB) and wheat bran (WB) and found to produce a multienzyme comprised of EG, BGL and Xyl. Under SSF of SB, the strains MK-157 and MK-118 were cultivated along with a pectinolytic strain, Geotrichum candidum AA-15 that led to significant increase in the production of pectinase. Similarly, the production of multienzyme preparation by the strains MK-118, MK-157 and MK-160 was also studied under solid-state fermentation (SSF) of peels of Citrus limetta (CL). The parameters affecting multienzyme preparation were studied by employing statistical tools, Plackett-Burman Design and Box-Behnken Design. The data inferred that the multienzyme preparation was able to efficiently hydrolyze a variety of pectin-rich and cellulose-rich LC substrates. Moreover, the preparation was also found suitable to be applied for the clarification of orange juice. Ethanol production and dye adsorption ability of strain MK-157 of S. cerevisiae, MK-118 and MK-160 of C. tropicalis were also evaluated. All the three strains produced ~5% of ethanol and absorbed more than 90% of an azo dye, congo red from aqueous solution. Therefore, the strains may appear as suitable candidate for future biotechnological applications.
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ڈاکٹر سید عبدالحفیظ مرحوم عامل بالحدیث تھے، ایک زمانے میں آل انڈیا جمعیتہ اہل حدیث کے امیر بھی تھے، عقیدہ و مسلک میں پختگی کے باوجود ان میں عصبیت نہ تھی، وہ مسلمانوں کے اجتماعی مسائل میں دوسرے فرقہ کے لوگوں کے...

Shrinking Civic Space in Pakistan: Response and Strategies of the Civil Society

This paper focuses the issue of shrinking civic space in Pakistan. The study presents civil society activists’ responses on this issue, highlights their perception, present and future strategies to address this issue, and their effectiveness, as such, as well. Pakistan presents a unique case due to its involvement in the ‘war on terror’ and the consequences being faced by both the state and society at large. Present shrinking of civil society action is directly linked with it. In an attempt to grapple with the problems emerging from ‘war on terror’, the overgrown state is encroaching upon citizens’ space, thus denying the civil society to play its due role which can provide safety for the state as well. The preferred strategies of the NGOs include lobbying with parliamentarians and mobilizing the citizenry about the situation.

Evaluation of Biological Potential, Elemental Profiling and Gcms Based Metabolomics of Some Selected Grasses of Bahawalpur, Punjab Province, Pakistan

Pakistan is enriched with natural flora comprising of unique wild and cultivated species utilized predominately by humans and animals. Bahawalpur region is in one of the nine divisions of the Punjab province in Pakistan established near the Sutlej River and comprises of many valuable species including grasses. Grasses possess remarkable economic and medicinal importance. All the cereal crops (maize, wheat, rice, barley) are also cultivated grasses. Many grasses are also used as a source of medicines as these are cheap, non-toxic and easily accessible. Hence, it is of keen interest to explore the native grasses of Bahawalpur region so that they can be used as a source of medicine and dietary fibre.In the present study, seventeen grasses were selected and their extracts were prepared in four solvents depending upon the polarity. Biological potential, elements and volatile compounds present in these extracts were evaluated. Initially, phytochemical tests were done to confirm the presence of different secondary metabolites. Total phenolic and flavonoid contents were determined spectrophotometrically which were detected in all extracts in varying concentrations. Highest phenolic contents were displayed in the methanol extracts of Ochthocloa compressa and Saccharum spontaneum (263.345 ± 16.35 mg GAE/g and 242.071 ± 20.63 mg GAE/g) while highest flavonoids contents were found in the ethanol extract of D. annulatum (47.023 mg QE/g) and the methanol extract of C. citratus (38.887 ± 2.19 mg QE/g). Antioxidant potential was determined via six different methods and the activity index was calculated. Results revealed that species which showed highest phenolic and flavonoid contents also exhibit highest antioxidant potential.Similarly, antimicrobial potential of all selected extracts was checked using disc diffusion assay which revealed somewhat weak to moderate antimicrobial potential against selected pathogens. So, cytotoxic potential was carried out to observe the toxicity potential of selected species. Among all species, O. compressa n-hexane extract showed highest cytotoxic potential with LC50 value of 2.80 µg/mL. All other species also displayed remarkable cytotoxic potential against brine shrimps. DNA damage protection assay was performed which revealed that ethanol and methanol extracts were more ix effective against DNA damage protection while acetone and n-hexane extracts did not show good activity. All inclusive, methanol extracts displayed significant biological potential as compared to the other extracts so they were further selected to examine antihemolytic potential of the plants. Methanol extracts of C. citratus (96.163 % inhibition), S. spontaneum (94.667 % inhibition), O. compressa (65.821 % inhibition) and D. annulatum (60.423 % inhibition) showed remarkable anti-hemolytic potential. Antihemolyticpotential of these species was found to be linked with the antioxidant potential and phenolic and flavonoid compounds. Strong anti-hemolytic and antioxidant activity of these plants suggests promising role in treating different diseases.Moreover, elemental profiling was done using ICP-MS and metabolomic studies were carried out using GC-MS. Results revealed the presence of seven essential and eighteen non-essential elements. Essential elements were found in decreasing order of potassium > magnesium > sodium > calcium > iron > manganese > zinc. Most of the non-essential elements were present within the permissible limit set by WHO which showed that the species are safe to use. GC-MS studies revealed the presence of more than 100 compounds in different concentrations. Decane (4.136 minutes) and m-cresol (5.46 minutes) were noted at minimum retention time in most of the species while Z-9hexadecenal (29.44 minutes) and 8, 11, 14-docosatrienoic acid, methyl ester (29.421 minutes) were identified at maximum retention time in most of the species. Total seventeen fatty acids and almost eighty-one different hydrocarbons were identified. Besides these, some monoterpenoids and diterpenoids were also detected in some species. Some of these compounds are known to possess cytotoxic potential while some of these compounds exhibit antimicrobial and antioxidant potential. Hence, these compounds are considerably involved in biological activities.In the end, individual organs of three species (S. halepense, D. annulatum and I. cylindrica) were investigated for further cell wall analysis. Acid-digestion of cell wall fractions revealed that xylose, arabinose, glucose and some traces of galactans are present more strongly in the aerial parts of selected species than the underground parts. Lichenase digestion confirmed that cellotrisoses exceeds cellotetroses and cellobioses in the cell wall of grasses. Dot-blot assay was done using eight commercial antibodies and comparison was made among dialysed and non-dialysed samples. Results revealed that x MLG, xylans, xyloglucans, arabinoxylan and glucoronoxylan were abundantly present in the sodium hydroxide extracts of non-dialysed samples while pachyman and mannan were not detected in significant concentrations. Some galactans were noted in the imidazole extracts of all fractions which showed the presence of pectins. Dialysed samples were not found effective to isolate hemi-celluloses from the fractions. Altogether, aerial parts possess more hemi-celluloses than the underground parts of plants.It is concluded that among all selected grass species, C. citratus, S. spontaneum, O. compressa and D. annulatum possess significant antioxidant, anti-hemolytic and cytotoxic potential. Overall, all species exhibited a variety of elements and compounds which are responsible for their biological activities. Moreover, these species can also be used as a biological marker. Cell wall analysis confirmed the presence of glycans in the aerial parts of plants which can be used as a dietary fibre and in different fibre industries. In future, in vivo studies should be carried out to confirm the medicinal value of these plants and compound isolation and microarray based profiling should be done to confirm the presence of non-volatile compounds and cell wall glycans.