Sporulation of Metarhizium anisopliae in solid-state fermentation with forced aeration (original) (raw)
Related papers
Characterization of growth and sporulation of Metarhizium anisopliae in solid-substrate fermentation
Enzyme and Microbial Technology, 1996
The entomopathogenic fungus Metarhizium anisopliae was cultivated by solid-substrate fermentation both with and without forced aeration using a medium based on a mixture of rice bran and rice husk: the water activity wasfired at an initial value of 0.998. An equation to describe the growth and sporulation processes was derived from stoichiometric considerations. By means of elemental mass balances and using the concept of c-mole, the stoichiometric coefJicients of the growth equation were determined. It was concluded that under the culture conditions tested, M. anisopliae can grow at a maximum specific growth rate of 0.08 h-'. After 90-100 h of culture when growth has stopped, a spore yield of 2.3 x 10" spores g-' rice bran was obtained. This is as high as 80.4% of the maximum theoretical value. The heat generated during the culture did not affect growth and sporulation since, even when high initial amounts of solids were used, no desiccation was observed. Nevertheless, the yields obtained under these conditions suggested the appearance of another type of growth limitation not related to substrate consumption.
Process Biochemistry, 2005
A range of experiments was performed to establish optimum aeration and moisture content conditions for sporulation of Metarhizium anisopliae IMI330189 in solid substrate fermentation (SSF). The cultivation was performed in column bioreactors. The following conclusions from the experimental results obtained have been made: (1) Forced aertion is not crucial for sporulation of M. anisopliae IMI330189 (no increase in sporulation has been achieved with increase in aeration). (2) Changes in moisture content affect sporulation, the optimum being at 57-58% moisture content. (3) No interaction between the two factors studied was observed.
Present investigation was carried out to find out the effect of different parameters on growth and sporulation of Metarhizium anisopliae . Amongst nine media tested SDA+Y media was found most suitable for growth and sporulation of M.anisopliae. The temperature 25 0 C followed by room temperature was found most suitable. During the incubation of mass culture relative humidity of 85% favours the growth and sporulation. The best pH 5.5 was found best and recorded maximum mycelial growth with abundant sporulation.
High level of sporulation ofMetarhizium anisopliae in a medium containing by-products
Applied Microbiology and Biotechnology, 1990
Solid-state fermentation of rice bran or ricebran-husk mixtures by Metarhizium anisopliae proved to be highly successful in spore yield. Optimum sporulation response on bran medium occurred when the initial water activity values ranged from 0.982 to 0.999. When bran was supplemented with 50% rice husk, the spore yield almost doubled, but a narrower initial water activity range (0.997-0.999) was optimum. Under these conditions, spore yields were 5-15 times higher (depending on the strain) than those currently obtained on the basis of rice grain fermentations. On the basis of rice grain fermentations, M. anisopliae spores are currently produced in Brazil on an industrial scale by business companies, grower cooperatives and plantation owners, yielding about 10% fungal mass (Alves 1986), which is considered economically viable. Since rice is commercially valuable as human food, it may be possible to device some cheaper and more highly productive methods for producing M. anisopliae spores than those based on rice grain fermentations. In this report we describe a novel and highly productive process for growth and sporulation of M. anisopliae based on rice-bran-husk fermentation.
Suitability of Media and Containers for Mass Production of Metarhizium anisopliae
Broken rice proved to be the most ideal substrate for mass production with higher conidial productivity and yield followed by sorghum. Conidial yield from maize, wheat and chickpea did not differ to discriminate the substrate superiority. Among the low cost liquid medium evaluated for mass production coconut water and rice gruel fortified with yeast (1%) supported the growth and conidial production better than molasses fortified with yeast (1%). Fungus growth was fast in saline and flat bottles resulting in shortest time lag between seeding and harvest (15-16 days) of conidia with higher roductivity and lowest contamination problem.
Biotechnology and Bioengineering, 1987
The development of Penicillium roqueforti on buckwheat seeds proceeds roughly into four steps, involving a lag phase and three growth phases. First, it appears as a spore germination and external colonization of the grains by the mycelium. Then, mainly external sporulation and internal colonization of the seeds occur and finally internal sporulation takes place. The stoichiometry of the growth and the sporulation is established. Kinetic experiments performed in a fixed bed reactor show that the growth of the microorganism (biomass production) may be estimated by the protein content of the medium. This growth occurs with a very low pmax value close to 0.030 h-'. The chitin content of the medium is an indicator of the sporulation, just as the metabolic liquor (mainly water) produced during the course of a cultivation. The values of the observed respiratory quotient are close to those predicted by stoichiometry.
2021
The effect of temperature on the mycelial growth of two isolates of Metarhizium anisopliae (Metch.) Sorok. (Hypocreales, Clavicipitaceae) was evaluated in vitro on PDA growth medium, by measuring the diameter of the fungal colonies, at the following temperature values: 5, 10, 15, 20, 25, 30, 35 and 40 °C, over 14 days under constant conditions. The data obtained were used for the calculation of the growth rate (mm/day) using linear regression. The representation of the values corresponding to the minimum, optimal and maximum temperature of vegetative growth was made by a curve described by a mathematical function, a modified beta (ß) function. The lowest temperatures at which growth occurs are 7 and 10°C, the highest is 35.7°C; temperature at which the most growth occurs, as indicated by the measurements, was distributed over a range of temperatures from 22.9 to 31°C.
Conidia production of Metarhizium anisopliae in bags and packed column bioreactors
Current biotechnology, 2018
Background: Metarhizium anisopliae controls insect pest populations and commercial formulations are based on conidia, regularly produced in plastic bags using rice grains as substrate. This process is labour-intensive and difficult to control; optimisation represents a current problem, even using different types of bioreactors. However, comparisons between Metarhizium conidia production in bags and packed columns are scarce. Objective: The aim of this study was to evaluate the age of the inoculum and two different type of bioreactors on the production of conidia from Metarhizium anisopliae. Method: Metarhizium anisopliae strain CP-OAX was used for conidia production (inoculum of 19 or 25 days old) using steamed rice as substrate either in plastic bags or packed bed bioreactors, the latter with different sizes with air supply. Results: Up to 30% higher conidia yields were obtained in the packed bed bioreactor after 7 days, using a 25 days old inoculum. Respirometric analysis on the packed bed bioreactor determined lag values from 49.08 to 55.23 h and maximum CO2 production rate of 0.295 ± 0.015 mg gidm-1 h-1 ; maximum sporulation occurred at 56.7 h. Conclusion: Both inoculum age and bioreactor geometry affect conidia production and productivity. The packed column bioreactor allowed higher conidia production and productivity. Air supply at the high scale packed column bioreactor allows metabolic heat removal to maintain isothermal conditions. In addition, the packed bed bioreactor presents advantages, such as reproducibility, the possibility of scaling-up and monitoring the process in terms of temperature and CO2 production.
Applied Microbiology and Biotechnology, 1992
Both growth and sporulation increase linearly according to the initial water content of the solid substrate when Penicillium roquefortii is cultivated on buckwheat seeds. This indicates that water is the limiting factor for fungal development since neither carbon nor nitrogen sources were exhausted during these experiments. This feature validates the concept of available water for fungal growth, defined as initial water content of substrate minus its residual water content when vegetative growth stops. An efficient methodology, based on drawing a regression line of mycelium dry weight production as a function of the initial water content of substrate is presented; it allows estimation of both available water and water content of mycelium. Results show that growth stops when the residual water in the substrate is close to 0.52 g H20/g initial dry matter, corresponding to a water activity (aw) close to 0.96, and that the initial water content in mycelium is near 76%. Thus, both aw and water content of the substrate have to be taken into account during the course of solid-state cultivations.
Effect of agitation intensities on fungal morphology of submerged fermentation
Biotechnology and Bioengineering, 1997
Both parallel fermentations with Aspergillus awamori (CBS 115.52) and a literature study on several fungi have been carried out to determine a relation between fungal morphology and agitation intensity. The studied parameters include hyphal length, pellet size, surface structure or so-called hairy length of pellets, and dry mass per-wet-pellet volume at different specific energy dissipation rates. The literature data from different strains, different fermenters, and different cultivation conditions can be summarized to say that the main mean hyphal length is proportional to the specific energy dissipation rate according to a power function with an exponent of −0.25 ± 0.08. Fermentations with identical inocula showed that pellet size was also a function of the specific energy dissipation rate and proportional to the specific energy dissipation rate to an exponent of −0.16 ± 0.03. Based on the experimental observations, we propose the following mechanism of pellet damage during submerged cultivation in stirred fermenters. Interaction between mechanical forces and pellets results in the hyphal chip-off from the pellet outer zone instead of the breakup of pellets. By this mechanism, the extension of the hyphae or hair from pellets is restricted so that the size of pellets is related to the specific energy dissipation rate. Hyphae chipped off from pellets contribute free filamentous mycelia and reseed their growth. So the fraction of filamentous mycelial mass in the total biomass is related to the specific energy dissipation rate as well.