This is a very intersting question. I hope this is an area where every body has face this problem. I personally in my case have faced this scale up issue. It is very easy when we grow microorganisms in lab scale. This is because, they are under sophisticated observations of growth and other such parameters. When we use for a large scale application say for example in heap bioleaching, almost the reactor is open to the atmosphere where several problems are seen.

You can refer to my recent article published in Hydrometallurgy " Insights into heap bioleaching of chalcopyrite ores- A pilot scale study", 2012, 125-126, 157-165.

Biofilm reactors are simple and offer higher productivities than other reactor systems. Inside a biofilm reactor, bacteria cells grow within a structural matrix and adhere to a surface, and the reactors can be operated for long period of times. This would help in reducing the process cost. These reactors are already in use for wastewater treatment and acetic acid/vinegar production by fermentation. It is clear that their use at bench scale has been consistently increasing for the production of various other chemicals. As productivities in these simple biofilm reactors are high, their full potential should be employed for biotechnological/biological conversion processes.Overall,it can treat large volumes of water or fluid at high rates, creating an efficient industrial process

Acid thiobacillus ferrooxidans was used in fixed-film bioreactors to oxidize ferrous sulfate to ferric sulfate. Glas beads, ion-exchange resin, and activated-carbon particles were tested as support matrix materials. Activated carbon displayed the most suitable characteristics for use as support matrix of T. ferrooxidans fixed-film formation. The reactors were operated within a pH range of 1.35 to 1.5, which effectively reduced the amount of ferric iron precipitation and eliminated diffusion control of mass transfer due to precipitation. The activated-carbon packed-bed reactor displayed the most favorable biomass holdup and kinetic performance related to ferrous sulfate oxidation.

Scale-up of Bioleaching using fungus offer problems during the down-stream processing due to the cumbersome loads of biomass produced. The safe disposal of the huge fungal mass remains a challenge. Reuse of the biomass as inoculum can be a alternate solution for this issue.

Also, the re-growth of fungal spores present in the spent culture filtrate (containing bio-organic-acids)pose a problem as they adhere to the ore material and hinder the leaching process. I would like to some have suugestions about how to inhibit the re-growth?

Good issue to talk about. Using fungus as a means of bioleaching as Jacintha suggested is limited to to lab scale applications. Yes it is true that if you filter the fungus from the media it still regrows which offers a problem when you want only bioacids without fungus. This factor still has, in advance, scale up problems. I think the filtration method before re-growth will work but it can be considered as a tedious process.

This is a very good and relevant question. Similar problems are being faced while growing algae in large scale open raceway ponds. It is very easy to cultivate algae in laboratory condition. However when we scale up the major problem is contamination.

Growth of Aerobic and anaerobic biomass in the batch and continuous system uses the support for the biomass: silica, polyacrylamide gel, polyurethane, calcium alginate, glutaraldehyde, charcoal and zeolites. The use of support for the biomass increases the development of the microorganisms. Different parameters: time, pH, temperature, HRT, toxicity and stirring speed are being studied. The techniques for determination of parameters for anaerobic are such as, chemical oxygen demand (COD), alkalinity, methane production, total solids (TSS), volatile solids (VSS), volatile fatty acids (VFA) concentrations, and for the aerobics, the biomass concentration using % of transmittance, McFarland nephelometer, isolation, macroscopic and microscopic characterization, growth kinetics, in batch and continuous system.

.Successful culture maintenance in raceway pond requires continuous monitoring. The most basic kind of monitoring is the regular microscopic examination to detect any abnormal morphological changes and the presence of contaminating organisms such as other algae and protozoa. Routine tests of nutrient concentration of the pond must also be carried out to avoid unexpected nutrient deficiencies. Regular monitoring of changes in pH and O2 levels in the pond over the day can also be a useful early warning system.

When considered for scaling up of microbial cultures desiging of reactors are very important. In the case of heap bioleaching, heaps are engineered properly. Based on the laboratory and bench scale studies scale up issues are considered. A bacterial reactor also needs proper engineering aspects. Also contamination plays a crucial role in originality of the microbes used in the process.

The moving bed biofilm reactor (MBBR) use plastic biofilm carriers of a unique design, to maximize the active biofilm surface area in the reactors. Reactors have insignificant headloss, no need for periodic backwashing and no susceptibility for clogging.MBBRs have been successfully used for biological treatment of drinking water as well as for water treatment in fish farms. The MBBR process offered a very compact treatment solution and had both the lowest investment costs and the lowest total annual costs.

A new generation of high load, efficient biofilm reactors (including BAS, ESB and IC

reactors) are operating throughout the world with several full-scale applications for industrial and municipal waste-water treatment. The remaining challenge in the

engineering of these systems is directed towards the control of biofilm structure and morphology, which depends on, and at the same time affects, the reactor

hydrodynamics and mass-transfer characteristics. New modelling tools are presently being developed to support experimental findings in the prediction of biofilm

structural and morphological properties

Biofilm reactors are good for waste water treatment. Can this technology be used for waste water treatment of algae raceway pond after harvesting of algae so that we can reuse the water for growing algae again ?

Culture pelleting and morphology has a strong influence on process productivity and success for fungal and filamentous bacterial cultures.On-line measurements were utilized to indirectly evaluate the cultivation impact of changes in medium and process development. Key laboratory to pilot plant scale-up issues also were identified and often addressed in subsequent cultivations.Examples of approaches included the use of additives to minimize pelleting in inoculum shake flasks, the use of large-volume frozen bagged inoculum obtained from agitated seed fermentors, and variations in production medium composition and fermentor operating conditions.

Microbial consortia play important roles in many traditional industrial bioprocesses such as for food and beverage production, waste material treatment and biogas production.The use of defined or minimal microbial consortia involving a few species seems to be promising. They can well serve as model system(s) for method and technology development .

More than contamination, critical aspects used when scaling up a bioprocess are the hydrodynamic conditions in each scale. It really depends on the bioreactor geometry and mixing power in order to guarantee favorable and stable conditions for microorganism. Some Reynolds criteria are used, avoiding cellular stress or inhibition.

In addition to the point made by Carlos, the larger the scale the more difficult it is to ensure homogeneity and to avoid dead zones

Scale up is mainly influenced by mode of aeration-agitation, media composition and sterilisation. These are mainly the factors that are different at lower and higher scale making scale-up process a difficult task. We need to work on these.

Microbial consortia are industrially applied for wastewater treatment, biogas production and biological soil remediation.In comparison to the many biotechnological processes based on the pure cultures, examples for the application of mixed cultures or microbial consortia in the production of chemicals are relatively few. However, bioprocesses involving microbial consortia were and are still the predominant practice for traditional food and beverage industries.From an engineering perspective, new types of bioreactor and operation strategies are needed for a successful use of mixed cultures or microbial consortia for production purposes.

http://: 10.1002/elsc.201000111

I have worked in an industrial heap bioleaching operation. Now interestingly, as everyone has discussed, it is indeed a great problem when we scale up. As in my case where bacterial solution is prepared at once in some cubic meters in open bioreactors under natural environmental conditions, the volume is affected by evaporation losses which has to be daily monitored and compensated with appropriate water or media. Also homogenity is a issue. Still we have tried to minimize the problems and are still working on to provide an easy and faster way to recover metal values using microbial biotechnology.

I want to scale up the process of production of thiobacillus thioxidans. What type of fermator be suitable ?