Understanding the morphology of fungi

Abstract

Filamentous fungi comprise an industrially very important collection of microorganisms, since they are used for the production of a wide variety of products ranging from primary metabolites to secondary metabolites and further on to industrial enzymes (such as proteases, lipases and antibiotics). It is known that fungal morphology is often considered as one of the key parameters in industrial production. For the production of fungal metabolite products, the desired morphology varies from one product to another. Many parameters affect the morphology of fungi during the process of fermentation, among them speed of agitation, speci®c growth rate, dissolved oxygen, number of spores or conidia per liter of fermentation broth are important and should be considered when higher yield is desired in the process. It is, therefore, of considerable importance to understand the mechanism underlying the morphology of the cell, its growth and product formation by ®lamentous fungi. Such knowledge may be used in the optimization of the microbial process. Several literatures with various fungi to study their morphology, relating enzyme or product production to the character of the fungi in the study is reviewed. It is also considered that how the process parameters affects the morphology. The aim of this communication is to review the relevant literature to understand the morphology of ®lamentous fungi. List of symbols bhyphal density, lm/tip D i impeller diameter, m D pellet diameter (in Eqs. 4 and 5), mm D r dilution rate, h )1 k constant, number of section used for branching (in Eq. 7) K c constant K r constant (in Eq. 5) K r linear colony radial growth rate (in Eq. 1), lm/h L e mean length of main hyphae, lm L e *mean dimensionless length, lm L t mean total length of hyphae, lm L hgu mean length of hyphal growth unit, lm M 0 dry weight of mycelia at time t 0 , g M 1 dry weight of mycelia at time t 1 , g n number of disrupted pellets N impeller speed, h )

Symbiotic and endophytic fungi as biocontrols against cocoa (Theobroma cacao L.) phytopathogens

“…Macro and micro characteristics of secondary phytopathogens are also shown in Figure 1 (3A-3F), coinciding with previous reports by Pazouki & Panda (17). Molecular characterization allowed determining that the isolated strains corresponded to the species A. flavus and F. solani, respectively, reported by Mounjouenpou et al (14).…”

Utilization of orange peel, a food industrial waste, in the production of exo-polygalacturonase by pellet forming Aspergillus sojae

“…This phenomenon was discussed in the previous reports of our group and A. sojae was shown to form pellets in submerged culture under the optimized conditions [19,20,32]; whereas in another study, the same organism formed small mycelial clumps (small groups of entangled mycelia) in the presence of OP and sugar beet syrup as substrates [8]. It is well known that inoculum size is one of the main factors influencing the growth form and product formation in fungal cultures [22,39,40]. Therefore, the effect of inoculated spore concentration on the morphology and exo-PG activity was investigated in OP-AS and in M2 medium, in an effort to obtain a pellet forming, less viscous and high exo-PG producing condition.…”

“…Growth form in the former case created mixing problems in the bioreactor, which was apparent by the poorly mixed zones in the broth in high inoculum size culture. Inefficient mixing and probably higher amount of biomass in the high inoculum case resulted in poor aeration of the broth, as can be deduced by the lower dissolved O 2 profile [22]. Consequently, enzyme production was impaired in this culture.…”

“…Desired morphology depends on the fungus and the product, e.g., penicillin production by P. chrysogenum requires free mycelia, while pellets are required for citric acid production by A. niger [22,23]. The main factors affecting the morphology are: type of strain, pH, temperature, medium composition, aeration, and inoculum size besides the genetic factors.…”

Effects of Aspergillus niger inoculum concentration upon the kinetics of starchy wastewater pretreatment in a tanks-in-series bioreactor under transitory conditions

“…Maintenance of residual biomass in reactors R 1 , R 3 and R 5 when the 3.6 g/l fungal biomass concentration was used could be explained by the morphological transformation of the fungal biomass from small pellets to filaments and gross pellets as observed in the reactor system. This fungal morphological transformation is well documented and is attributed to inoculum concentration, pH and sheer stress (Tung et al, 2004;Pazouki and Panda, 2000). Biomass in filament and gross pellet forms could not be transferred to the adjacent reactor because of its size or adsorption on reactor constituents.…”