| dc.description.abstract | Generally, antibiotics production relies on glucose or lactose as carbon and energy
source. Alternatively, available raw materials such as agro-wastes have been used
successfully as substrates in growth of micro-fungi. The growth of different fungi has
been shown to differ with various substrates used. Therefore, there is need to select
suitable agro-waste substrates for a given fungus. Moreover, natural fungi can be
isolated from dumpsite soils instead of using a standard-fungi in production of
antibiotics. To achieve efficient production of antibiotics, optimum growth conditions
of specific fungi need to be determined. The objectives of this study were to isolate and
characterise secondary metabolites produced by Acremonium spp from dumpsite soils,
optimising the growth conditions suitable for the production of the cephalosporin and
determine its antibacterial properties in-vitro. Isolation of Acremonium spp was done
by spread plate method on potato dextrose agar treated with vancomycin to inhibit any
bacterial growth. Acremonium spp colonies were characterised using their macroscopic
and microscopic features. Response Surface Methodology was used to determine the
optimal growth conditions (temperature, pH and substrates). Growth conditions of
Acremonium spp were optimised using three levels of each input variables
(temperatures range of 25⁰ C, 28⁰ C and 31⁰ C; pH of 5.5, 6.5 and 7.5; substrates
(wheat bran and corn cob, and glucose and lactose used as control). The antibacterial
activity of the chloroform-extract was tested in-vitro against three bacterial strains;
Escherichia coli ATCC 25922, Salmonella typhi ATCC 6539 and Staphylococcus
aureus ATCC 25923. Data was collected on optimal growth conditions, yield of
mycelia biomass and zones of inhibition. Data collected were subjected to one-way
ANOVA to determine significant variation between treatments (levels of pH,
temperature and substrates) on mycelial biomass yield and, antibacterial activity of the
chloroform-extract using SAS version 9.4. Significant means were separated using LSD
at α = 0.05. This study revealed that serial dilutions of 102
and 103 were suitable for the
isolation of the fungus. The findings of this study revealed that treatments had
significant (p < 0.05) effect on mycelia biomass yield. Generally, corn cob gave the
highest mycelia biomass yield, while lactose gave the lowest yield. Corn cob yielded a
mycelia biomass ranging from 0.90 g – 2.45 g while wheat bran yielded mycelia
biomass ranging from 0.64 g – 1.77 g. The results of this study revealed that, the optimal
growth conditions for Acremonium spp when using wheat bran as a substrate are, a pH
of 7.32, temperature 28.24 ⁰ C and 5.88 g of wheat bran, while, using corn cob as a
substrate are, a pH of 7.6, temperature 28.36 ⁰ C and 5.66 g of corn cob per 50 ml
fermentative media. Using the optimum growth conditions, 629.69 mg/L and 559.68
mg/L amount of cephalosporin for crude and purified extract, respectively, was
achieved. In-vitro antibacterial activity of the chloroform-extract at 6 mg/ml, 12 mg/ml
and 18 mg/ml tested against E. coli, S. typhi and S. aureus showed zones of inhibition.
TE, AMP, GEN, S, SX, COT NIT and NA were used as the positive controls while
chloroform was used as the negative control to confirm sterility of the paper discs used.
The study also revealed that some of the positive controls (TE, COT and SX) on E. coli
gave significantly higher zones of inhibition than chloroform-extract at 6 mg/ml.
Resistance to AMP was observed in all the bacterial strains. The study concluded that
it is possible to isolate native Acremonium spp from dumpsite soils and optimisation of
fungi growth conditions result to high yield of cephalosporin. The study recommends
bioprocessing industries to consider utilising agricultural wastes as source of growth
substrates in production of cephalosporin. This will not only curb environmental
pollution but also bio-converse wastes into wealth and provide alternative cost-effective
substrates for production of cephalosporin antibiotics. | en_US |
