Isolation, Characterization And Optimization Of Conditions For Pigment Producing Fungal Isolates From Jibat Forest Soils

Abstract

Due to the detrimental consequences of chemically manufactured colorants on human health and the environment, natural colors are becoming increasingly sought. Microbial pigments have been given priority over all other naturally occurring coloring sources, owing to the ease with which microbes may be handled and the production process'. The main aim of this research was to isolate, characterize and optimize of conditions for pigment producing fungal isolates from rhizosphere soil of some tree in Jibat forest. The soil samples purposively were collected from eight different trees and taken to the Biology laboratory at Ambo University's, College of Natural and Computational Sciences, Department of Biology were they serially diluted from 10-1 to 10-5 then pour plated on mycological media and incubated at 28°C.Colonies of the fungal isolates were enumerated after 5 days of incubation and two red pigmented fungal isolates (S5I23 and S7I3) were chosen for further characterization and experimental studies. The effects of various nutritional and environmental variables on growth and the production of extracellular and intracellular pigments were investigated. The extractability of intracellular pigments from fungal mycelium by different solvents was investigated. The effects of different conditions on pigment production potential of the selected fungal isolates were evaluated by taking the optimal density by using Uv-visible spectrophotometer. SPSS for window version 25 was used to analyze all the quantitative data collected. The results of this study indicate that only 17 of the 56 fungal isolates from rhizosphere soil samples were pigmented, while the rest were non-pigmented. The two fungal isolates were provisionally identified as Fusarium after cultural and morphological characterization. In S5I23, fructose favored maximum extracellular (OD 1.056) and intracellular (OD 1.514) pigmentation, while lactose was limited extracellular (OD 0.100) and intracellular (OD 0.989). In S7I3, glucose favored maximum extracellular (OD 1.551) and intracellular (OD 1.306), while sorbitol inhibited growth and pigmentation extracellular (OD 0.055) and intracellular (OD 0.963). In S5I23, yeast extract stimulated growth and pigmentation extracellular (OD 0.406) and intracellular (OD 2.943), whereas tryptone minimal growth and pigmentation extracellular (OD 0.131) and intracellular (OD 1.001). In S7I3, peptone stimulated growth and pigmentation extracellular (OD 0.758) and intracellular (OD 2.514), whereas sodium nitrate limited extracellular (OD 0.095) and intracellular (OD 1.710). In S5I23, incubation temperatures of 28°C encouraged extracellular (OD 0.492) and intracellular (OD 1.328) growth and pigmentation, whereas temperatures of 20°C were very limiting for both extracellular (OD 0.377) and intracellular (OD 0.963) growth and pigmentation. In S7I3, extracellular (OD 1.014) and intracellular (OD 2.519) growth and pigmentation were preferred at 28°C, but 20°C was extremely limiting for growth and pigmentation of fungal isolates in both extracellular (OD 0.174rpm) and intracellular (OD 1.717rpm).In S5I23, pH10 was stimulating for both extracellular (OD 1.256) and intracellular (OD 1.069) growth and pigmentation, whereas pH4.5 was limiting for both extracellular (OD 0.231rpm) and intracellular (OD 0.977) growth and pigmentation. In S7I3, PH7 was optimal for growth and pigmentation in both extracellular (OD 1.867) and intracellular (OD 2.521), while PH4.5 was extremely restricting for fungal isolates' growth and pigmentation in both extracellular (OD 0.204) and intracellular (OD 1.695). In S5I23, 0.5 percent salt concentration was preferable for extracellular (OD 2.183) and intracellular (OD 2.493) growth and pigmentation, whereas 5 percent was limiting for growth and pigmentation extracellular (OD 0.058) and intracellular (OD 0.976). In S7I3, 0.5 percent salt concentration was found to be acceptable for extracellular (OD 0.737) and intracellular (OD 2.399) growth and pigmentation, while 5 percent salt concentration was found to be limiting in both extracellular (OD 0.063) and intracellular (OD 1.641). Solvents such as methanol, acetone, and acidified methanol were appropriate in extracting pigment from both fungal isolates' cell biomass. Extracellular 300nm and intracellular 240nm red color compounds retrieved from S5I23; extracellular and intracellular 220nm red color compounds extracted from S7I3.The findings of this study clearly demonstrated that pigment-producing fungi are abundant in the rhizosphere of trees, capable of producing variety of color that can be employed in a wide range of industries.