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Title: Evaluation of plant based products for their suitability as bacteriological media
Authors: Khalil, Sadia
Keywords: Microbiology
Biology Micro
Issue Date: 2018
Publisher: University of Karachi, Karachi.
Abstract: Plants are rich source of nutrients, compounds of medicinal importance and other valuable products used in our daily life. For the last few years, interest has been developed to utilize plant-based products as substrates in the preparation of microbiological. Their distinctive features are very intriguing from the perspective of the economical effectiveness for developing countries like Pakistan. The present study was aimed at exploring suitability of some plant-based products available locally as bacteriological media or supplements in these media. To instigate this study, raw forms of 56 plant based products were purchased from local markets and fruit shops. Overall, 5.5% of selected plant materials belong to pulses/ lentils, 17.8% fruits, 37.5% vegetables. Furthermore, 39.2% non-edible or plant waste substrates were also included in the study. Plant materials were selected on the basis of nutritional value, cost, availability and personnel curiosity. A number of methods were used for the extraction of various plant based materials but decoction was found to be the most suitable as evidenced by the results. Thus decoction was used throughout in the study for the preparation of extracts from plantbased products. In the course of preliminary screening, great variations in the growth pattern of bacteria on plant extracts were observed, however on the basis of the extent of growth, availability, seasonal variations and clarity of medium the selection was carried out. The aqueous extracts of onion, potato, sugarcane peels, apple-peels, black eye beans, red eye beans, carrot, cluster beans and flat beans were included for further studies to evaluate their potential to promote the growth of clinical isolates. Lentils and onion extract based media were used for growing P. fluorescence P22YO5 whereas sugarcane, apple, grapes fruit peels, wheat straw and wheat bran for Bacillus subtilis KPS11. The extracts which showed promising results in the initial study were selected for further study. The combinations of extracts were assessed for bacterial growth enhancing ability. The data revealed that the extracts in combination resulted in enhancing the growth of bacteria when compared with the growth on individual extracts. However, combinations rendered medium less transparent. However, pH did not exert a profound effect on the growth and higher growth was achieved on natural extracts with varying pH, from slightly acidic to slightly basic. Generally a direct correlation was established between the growth and concentration of extracts. Surprisingly for few, maximum growth was obtained at relatively lower concentration of the extracts. In addition, the turbidity of more concentrated media was also undesirable therefore, clarity of medium was also a key concern in deciding final concentration along with the extent of growth. The extracts were supplemented with additional carbon and nitrogen sources and growth of bacteria was compared with the growth on non supplemented and reference media. Results depicted that yeast extract and ammonium nitrate among other nitrogen sources promoted the growth of selected clinical isolates. A positive effect of increasing glucose concentration in onion extract and apple peels extract was also observed. Certain noticeable changes were observed while growing bacteria on supplemented solid media, such as loss of swarming ability in case of P. mirabilis; the ability was not regained even after the supplementation of various concentrations of Tween 80. The colonies of P. aeruginosa were larger as compared to size of colonies on reference media with higher muckiness on extract-based solid media. As far as growth kinetics is concerned, the clinical isolates and B. subtilis KPS 11 growing in shaking flask culture revealed the length of log and lag phase of bacteria comparable, whether cultivated in extract-based media or reference media (NB and LB). The growth of P. fluorescence P22YO5 was also observed in the microbioreactor using flower plate. Higher cfu /mL was obtained in the extract media when compared with the results observed in shaking flask experiments either using plant extract media or in commercially available TSB medium. Pseudomonas fluorescence P22Y05 was tested for their ability to control Fusarium dry rot in three potato cultivars namely, russet norkotah, red norland and russet Burbank and were compared with the control. The reduction in the occurrence of dry rot by P. fluorescence P22Y05 was observed in both, shaking flask culture (51.2–81.8 %) as well as in microbioreactor (70.7–87.2 %). The cells produced in any of the plant extract-based media under each production method did not differ in efficacy from the cells produced in TSB or NB. Results of chemical analysis revealed the presence of higher Ca, Fe, Mg, and P contents in the media before than after biomass production, in almost all extract media tested, inoculated with P22YO5. The red lentil extract medium was found to contain highest Fe Cu, Mo and Zn contents. In all media, NH4–N concentration increased after the cultivation of P22Y05. Red lentil extract and TSB showed the highest NH4–N (52 and 53 mg/l), respectively before and 662 and 644 mg/l, respectively after cultivation. Plant extracts selected in this study, contain very low level of organic acid thus did not show any antibacterial activity. Results revealed variations in the metabolites production by KPS 11 in different media. Our results demonstrate that several plant-based media can produce large quantity of efficacious biomass of biocontrol strain, P. fluorescens P22Y05 and biofertilizer strain B. subtilis KPS11 comparable to that produced in commercially available media. Similarly, the plant extract based media were found to be equally effective in comparison with reference media for the growth of clinically important bacteria. The potential of plant extract-based media to produce biomass and other metabolites of interest of other groups of microorganisms is a very important and crucial area in the study of microbiology. Moreover, further studies are required to be directed on differential and selective aspects of these culture media to produce large quantity of biomass for various industrial purposes/applications.
Gov't Doc #: 18471
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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