Assessment of Aspergillus niger biofilm growth kinetics in minibioreactors by carbon dioxide evolution

Aspergillus niger ATCC 10864 was grown on bubble minicolumns aerated with pure oxygen either as biofilm or free-mycelium submerged systems. Growth kinetics was followed by estimating biomass from released carbon dioxide using a titration method and mathematical models. Submerged cultures showed increased endogenous respiration rates (0.0298 vs. 0.0004 g biomass/g biomass.h) possibly related to stress condition since this type of growth is not the natural way of life of A. niger. On the other hand, A. niger biofilm growth followed a logistic model having higher maximal specific growth rate than submerged cultures (0.061 vs. 0.045 h-1). This may be related to better mass transfer processes due to a channeled mycelial microstructure. Biofilm growth can be easily and reliable assessed by evaluating the CO2 released during the fermentation in minibioreactors.Key words: Aspergillus niger, biofilm, mathematical modeling, endogenous respiration, Cryo-SEM

Structural analysis of biofilms and pellets of Aspergillus niger by confocal laser scanning microscopy and cryo scanning electron microscopy

This work was supported by INCAGRO (Ministry of Agriculture, Peru) and CONCYTEC (Ministry of Education, Peru). The authors wish to thank CERTINTEX (Lima, Peru) for the use of its SEM facilities, and Mr. Gianangelo Nava (CERTINTEX) for his SEM technical assistance.Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica - Concyte

Induced Biofilm Cultivation Enhances Riboflavin Production by an Intertidally Derived Candida Famata

The aim of the investigation was to ascertain if surface attachment of Candida famata and aeration enhanced riboflavin production. A newly designed polymethylmethacrylate (PMMA) conico-cylindrical flask (CCF) holding eight equidistantly spaced rectangular strips mounted radially on a circular disk allowed comparison of riboflavin production between CCFs with hydrophobic surface (PMMA-CCF), hydrophilic glass surface (GS-CCF), and 500- ml Erlenmeyer flask (EF). Riboflavin production (mg/l) increased from 12.79 to 289.96, from 54.44 to 238.14, and from 36.98 to 158.71 in the GS-CCF, EF, and PMMA-CCF, respectively, when C. famata was grown as biofilm-induced cultures in contrast to traditional planktonic culture. Production was correlated with biofilm formation and planktonic growth was suppressed in cultivations that allowed higher biofilm formation. Enhanced aeration increased riboflavin production in hydrophilic vessels. Temporal pattern of biofilm progression based on two-channel fluorescence detection of extracellular polymeric substances and whole cells in a confocal laser scanning microscope followed by application of PHLIP and ImageJ volume viewer software demonstrated early maturity of a well-developed, stable biofilm on glass in contrast to PMMA surface. A strong correlation between hydrophilic reactor surface, aeration

The characteristics of Aspergillus fumigatus mycetoma development: is this a biofilm?

Aspergillus fumigatus is an increasingly prevalent opportunistic fungal pathogen of various immuno-compromised individuals. It has the ability to filament within the lungs forming dense intertwined mycelial balls. These morphological characteristics resemble those of microbial biofilms, which are matrix enclosed microbial populations, adherent to each other and/or to surfaces or interfaces. The purpose of this paper is to review some recent experiments that indicate the potential biofilm forming capacity of A. fumigatus in vitro. Initially it was established that conidial seeding density is important for stable biofilm development. In the optimized model conidial germination and filamentous growth characteristics were not observed until 8 h, after which a multi-cellular population expanded exponentially forming a thick structure (approx. 250 m). Calcofluor white staining of this revealed the presence of extracellular polymeric matrix material, which increased as the biofilm matured. Subsequent antifungal sensitivity testing of this structure showed that azoles, polyenes and echinocandins were ineffective in reducing the cellular viability at therapeutically attainable concentrations. Microarray and real-time PCR analysis demonstrated the up-regulation of AfuMDR4 during multicellular growth and development, which may account the recalcitrance observed. Overall, A. fumigatus appears to possess the classical elements of biofilm growth, namely multicellularity, matrix production and sessile resistance. This controversial approach to understanding the biology of A. fumigatus infection may provide crucial information on how to treat this pathogenic fungus more effectively

Fungal Biotechnology in Space: Why and How?

Fungi have been companions of mankind for millennia. Mushrooms inspired our eating culture, and yeasts and filamentous fungi were developed into highly efficient cell factories during the last 100 years to produce many products utilized in different industries worldwide. What more is to come in the next 100 years? We propose here that fungi can become important cell factories for life in space, especially regarding the filamentous fungus Aspergillus niger as the cutting-edge must-have for space travel in the twenty-first century and beyond. First, it is one of the most robust and efficient production systems used nowadays in industrial biotechnology. Second, it is a multipurpose cell factory that produces a diverse range of organic acids, proteins, enzymes and natural products. And third, it is a common fungal isolate of the International Space Station. A. niger could thus become an essential companion of astronauts for the autonomous production of food, enzymes and antibiotics during space travel. What needs to be done to achieve these visionary goals? In this chapter, we will discuss the opportunities of A. niger as a cell factory spanning from Earth to space. We summarize the current state of the art of A. niger biotechnology on Earth and discuss the general tools and technologies still in need of development to take a new step for mankind: space biotechnology