Distinctive behaviour of invertase in a thermophilic fungus, Thermomyces lanuginosus

Maheshwari, Ramesh; Balasubramanyam, P. V.; Palanivelu, Peramachi

doi:10.1007/bf00407798

Cited by 14 publications

(19 citation statements)

References 22 publications

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“…In T. lanuginosus (155) and also in Penicillium duponti (P. Palanivelu and R. Maheshwari, unpublished data), invertase was an inducible enzyme and its activity was very unstable in cell extracts. By contrast, invertase from mesophilic sources retained activity for long periods under storage conditions.…”

Section: Invertasementioning

confidence: 96%

Thermophilic Fungi: Their Physiology and Enzymes

Maheshwari

Bharadwaj

Bhat

2000

Microbiol Mol Biol Rev

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648

380

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SUMMARY Thermophilic fungi are a small assemblage in mycota that have a minimum temperature of growth at or above 20°C and a maximum temperature of growth extending up to 60 to 62°C. As the only representatives of eukaryotic organisms that can grow at temperatures above 45°C, the thermophilic fungi are valuable experimental systems for investigations of mechanisms that allow growth at moderately high temperature yet limit their growth beyond 60 to 62°C. Although widespread in terrestrial habitats, they have remained underexplored compared to thermophilic species of eubacteria and archaea. However, thermophilic fungi are potential sources of enzymes with scientific and commercial interests. This review, for the first time, compiles information on the physiology and enzymes of thermophilic fungi. Thermophilic fungi can be grown in minimal media with metabolic rates and growth yields comparable to those of mesophilic fungi. Studies of their growth kinetics, respiration, mixed-substrate utilization, nutrient uptake, and protein breakdown rate have provided some basic information not only on thermophilic fungi but also on filamentous fungi in general. Some species have the ability to grow at ambient temperatures if cultures are initiated with germinated spores or mycelial inoculum or if a nutritionally rich medium is used. Thermophilic fungi have a powerful ability to degrade polysaccharide constituents of biomass. The properties of their enzymes show differences not only among species but also among strains of the same species. Their extracellular enzymes display temperature optima for activity that are close to or above the optimum temperature for the growth of organism and, in general, are more heat stable than those of the mesophilic fungi. Some extracellular enzymes from thermophilic fungi are being produced commercially, and a few others have commercial prospects. Genes of thermophilic fungi encoding lipase, protease, xylanase, and cellulase have been cloned and overexpressed in heterologous fungi, and pure crystalline proteins have been obtained for elucidation of the mechanisms of their intrinsic thermostability and catalysis. By contrast, the thermal stability of the few intracellular enzymes that have been purified is comparable to or, in some cases, lower than that of enzymes from the mesophilic fungi. Although rigorous data are lacking, it appears that eukaryotic thermophily involves several mechanisms of stabilization of enzymes or optimization of their activity, with different mechanisms operating for different enzymes.

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Section: Invertasementioning

confidence: 96%

Thermophilic Fungi: Their Physiology and Enzymes

Maheshwari

Bharadwaj

Bhat

2000

Microbiol Mol Biol Rev

Self Cite

648

380

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“…Mycelial inocula were prepared by incubating spores in a glucose-asparagine medium on a gyratory shaker (240 rpm) at 50°C, as described by Maheshwari et al (16). For P. duponti, the medium was supplemented with 0.1% (wt/vol) yeast extract (Difco Laboratories, Detroit, Mich.).…”

Section: Methodsmentioning

confidence: 99%

“…The concentration of glucose in the culture filtrates was determined by the glucose oxidase-peroxidase method (20). The concentration of sucrose was determined by using a commercial preparation of purified invertase from Candida utilis, as described previously (16). Invertase from mycelia was extracted and assayed as described previously (16).…”

Section: Methodsmentioning

confidence: 99%

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Simultaneous utilization of glucose and sucrose by thermophilic fungi

Maheshwari

Balasubramanyam

1988

J Bacteriol

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The utilization of mixtures of glucose and sucrose at nonlimiting concentrations was studied in batch cultures of two common thermophilic fungi, Thermomyces lanuginosus and Penicilium duponti. The sucrose-utilizing enzymes (sucrose permease and invertase) in both fungi were inducible. Both sugars were used concurrently, regardless of their relative proportion in the mixture. At the optimal growth temperature (50C), T. lanuginosus utilized sucrose earlier than it did glucose, but at a suboptimal growth temperature (30°C) the two sugars were utilized at nearly comparable rates. The coutilization of the two sugars was most likely possible because (i) invertase was insensitive to catabolite repression by glucose, (ii) the activity and affinity of the glucose transport system were lowered when sucrose was included in the growth medium, and (iii) the activity of the glucose uptake system was also subject to repression by high concentrations of glucose itself. The concurrent utilization of the available carbon sources by thermophilic fungi might be an adaptive strategy for opportunistic growth in nature under conditions of low nutrient availability and thermal fluctuations in the environment.Since Monod (21) described the phenomenon of diauxy in bacteria, it has become generally accepted that, when supplied with a mixture of two carbohydrates, the microorganisms utilize one carbon source at a time; for example, glucose is utilized before lactose is. There has been virtually no study of mixed substrate utilization in fungi, although this situation is expected to occur often in nature. We investigated the ability of thermophilic fungi to utilize mixed carbon sources. Thermophilic fungi are commonly found in compost and soil (17). Their optimum growth and metabolic activity occur between 45 and 55°C (5, 23). It is believed that they are capable of opportunistic development in the surface layers of soil when the soil temperatures become favorable because of solar heating (13). We considered the possibility that one of the adaptive strategies of thermophilic fungi growth in the thermally fluctuating (25) and nutritionally poor environment of soil (9) might be their ability to utilize the available carbon sources rapidly and simultaneously. We report here on the ability of two unrelated species of thermophilic fungi to concurrently utilize glucose and sucrose when provided in combination under substrate-sufficient concentrations and on some of the mechanisms that underlie this behavior. MATERIALS AND METHODSOrganisms. Thermomyces lanuginosus Tsiklinsky RM-B (ATCC 44008) was used in all experiments. In some experiments, Penicillium duponti Griffon and Maublanc RM-D was also used. Both fungi were taken from our laboratory collection of thermophilic fungi.Culture conditions. Mycelial inocula were prepared by incubating spores in a glucose-asparagine medium on a gyratory shaker (240 rpm) at 50°C, as described by Maheshwari et al. (16). For P. duponti, the medium was supplemented with 0.1% (wt/vol) yeast extract (Difco Laboratori...

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“…(Fujita et al 1990). However, there are only few reports concerning the production of a b-fructofuranosidase from thermophilic fungi (Maheshwari et al 1983;Katapodis et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Induction and partial characterization of intracellular ? from Thermoascus aurantiacus and its application in the synthesis of 6-kestose

Katapodis

Christakopoulos

2004

World J Microbiol Biotechnol

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Production of b-fructofuranosidase from the thermophilic fungus Thermoascus aurantiacus was enhanced by optimization of the type of nitrogen source as well as the type and concentration of carbon source. Submerged batch cultivation in a laboratory bioreactor (7 l) using the optimized medium allowed the production of 85 mU/ml of b-fructofuranosidase. The enzyme showed both transfructosylating and hydrolytic activities and was optimally active at 60°C and pH 5.0. The enzyme showed the ability to catalyse the synthesis of 1-kestose and the reaction was maximized at 30% (w/v) initial sucrose concentration.

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Distinctive behaviour of invertase in a thermophilic fungus, Thermomyces lanuginosus

Cited by 14 publications

References 22 publications

Thermophilic Fungi: Their Physiology and Enzymes

Thermophilic Fungi: Their Physiology and Enzymes

Simultaneous utilization of glucose and sucrose by thermophilic fungi

Induction and partial characterization of intracellular ? from Thermoascus aurantiacus and its application in the synthesis of 6-kestose

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