ABSTRACT
Serratia marcescens (GBB151) was isolated and genetically modified for high-yielding pigment production capacitythat could be employed for industrial purposes. Ethidium bromide-induced mutagenesis of GBB151 resulted inthe generation of eight mutant isolates (GBB151Ea-GBB151Eh). The chemical mutants of S. marcescens obtainedproduced 5-fold more pigment than the wild-type organism. The wild-type GBB151 produced 413.9 unit/cell,while the mutant strains produced pigments with yields ranging from 841.7 to 2008.5 unit/cell. Random amplifiedpolymorphic deoxyribonucleic acid-polymerase chain reaction analysis showed different amplicons patterns of nativeas well as mutant derivatives. The factorial analysis diagram and the dendrogram showed a degree of dissimilarityamong the wild-type bacterial isolate GBB151 and its mutants. Mutant strains GBB151Ec and GBB151Ef wereclosest to the wild type as they appeared in the same quadrant. GBB151Ed which had lost its ability to producepigment was farthest and in the different quadrant to the wild type. These study provided insight into improvement inpigment production by manipulating genetic make-up of S. marcescens, thus meeting industrial demand.
ABSTRACT
This study isolated, screened, and identified a pectinase-producing fungus from a decomposing plant material. Italso cultured the isolated fungus under optimized conditions to obtain crude pectinase enzyme as well as purifiedand investigated the biochemical characteristics of the purified enzyme. The fungal strain was isolated on pectinasescreening agar medium containing 1% pectin and obtained a clear zone. It was identified as Aspergillus fumigatus andcultivated for enzyme production using banana, plantain, and orange peels as the solid substrate. Under optimizedconditions, a maximum of 3.52 U/ml pectinase activity was obtained at 65% moisture content after 144 h (6 days)of incubation period on orange peel, 1.5 ml inoculum, and 3% salt content. A. fumigatus pectinase was purified4.45-fold and a yield of 26.16% with a specific activity of 38.88 U/mg. The molecular weight determined on sodiumdodecyl sulfate (SDS-PAGE) was 31.6 kDa. The pectinase exhibited maximum activity at 60°C, optimum pH of 5.0,and stability at 40–50°C. The enzyme showed a preference for polygalacturonic acid as its primary substrate with aKM 3.08 mg/ml and Vmax of 1.61 U/ml. The enzyme was activated by 0.5 mM Na+, K+, and 1–5% toluene. The enzymeactivity was inhibited by metal cations; 20% ethanol, 4.0 mM SDS, and L-cysteine. The obtained results showed thatA. fumigatus pectinase could be a candidate for potential industrial and biotechnological application