Cultivation of biofilms

There are currently no recommendations or guidelines concerning the standardized cultivation of biofilms methods which give indications of practical efficacy are the most useful. Attempts have been made to unify procedures for determining the efficacy of biocides however, the findings of the available literature are difficult or impossible to compare. In principle, this can be described under several headings with respect to the duration of the investigations ... 

Vastly different methods are available for cultivation of biofilms. Basically, these can be described as either batch-mode or continuous mode methods. In batch studies, growth substrata in the form of coupons or glass slides are placed in e.g. Petri-dishes or other holders filled with medium. Under the action of undefined shear forces, investigations in so-called beaker reactors are conducted. A further test system which operates in batch mode and continues to become prominent is the miniaturized test system comprising microtitre plates, in which 96 wells enable the simulation of various experimental conditions simultaneously under static conditions (Geneveaux et al., 1996 O Toole et al., 1999). In general, biocide tests in batch systems are simpler to run, have shorter durations, and are very simple to carry out. Therefore, they are well-suited for initial comparisons or screenings of different biocides, or different concentrations and contact times of a particular biocide. 

Other cultivation strategies which were followed were the enrichment of picoplankton bacteria under a wide range of nutrient and incubation conditions [33], and isolation of biofilm bacteria that had grown in situ on artificial surfaces. 

Caldwell, D. E. 1995. Cultivation and study of biofilm communities. In Microbial Biofilms (H. Lappin-Scott and J. W. Costerton, Eds.), Plant and Microbial Biotechnology Research Series 5, pp. 64-79. Cambridge Univ. Press, Cambridge, UK. 

Venkatadri R, Irvine RL. Cultivation of Phanerochaete chrysosporium and production of lignin peroxidase in novel biofilm reactor systems hollow fiber reactor and silicone membrane reactor. Water Res 1993 27 591-596. 

Fig. 11.3. Fungal colonies of Coniosporium uncinatum, forming a network on a marble block surface. The formation of interconnecting hyphae and hyphal bundles seemingly represent an adaptation to survive under the hostile conditions on the mineral surface. Interconnected fungal biofilm often demonstrates the development of a complex and three-dimensional structure on the mineral surface (A, B), which frequently results in deeper penetration into the rock substrate (B). This elaborated network has been developed on the marble surface after only three months of laboratory cultivation.

Fig. 11.4. The development of the fungal network on the marble surface (Crimea, Ukraine). As demonstrated by scanning electron microscopy, these hyphae are accompanied by intensive bacterial growth on their surface (A) and thus probably are the pioneer organisms of subaerial biofilms. (B) oxalate crystal formation was observed only when the fungal colonies were cultivated subaerially or in sterile sand. Coverage of the colony with podzol soil blocked the biomineralization process (data not shown) probably by metabolic products of soil microorganisms.

Fig. 21 Top Schematic setup of an ultrasonically vibrating micropitted silicon surface. The cavitation chamber is filled with pure liquids or a cell cultivation liquid for biological assays. Bottom Temporal recording of a biofilm removed by microbubbles. The grey area with black dots is the zone covered by biofilm. The pit is indicated with a large black dot. Microbubbles can be identified as the blurred dark region surrounding the pit. Reproduced with permission from [110]. Copyright 2012 AIP Publishing...

Ozkan A, Kinney K, Katz L, Berberoglu H Reduction of water and energy requirement of algae cultivation using an algae biofilm photobioreactor, Bioresour Technol 114 542—548, 2012. 

Vandecandelaere I, Nercessian O, Faimali M, Segaert E, Mollica A, Achouak W, De Vos P, Vandamme P. Bacterial diversity of the cultivable fraction of a marine electroactive biofilm. Bioelectrochemistry. 2010 78(l) 62-6. doi 10.1016/j.bioelechem.2009.07.004. 

Several bioreactor designs are used to produce bioproducts, and include, but are not limited to batch reactors, fed-batch reactors, continuous cultivation reactors, plug flow reactors, recycle bioreactor systems, immobilized cell reactors, biofilm reactors, packed bed reactors, fluidized-bed reactors, and dialysis cultivation reactors (Williams 2002). These reactor types can contain either mixed or pure cultures, and can stimulate heterotrophic and/or phototrophic cellular functions depending on the specific reactor design. Additionally, these reactor schemes can be used to produce products directly, or to harvest biomass or other products for downstream processes. Due to the complex nature of bioreactors, particularly anaerobic digesters, the use of metagenomics is helpful to understand the physiology of such systems. 

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