Are there alternative methods of spore preparation?
Yes, including even more expensive production systems for conidia of beneficial fungi. The new MycoHarvester 6 (MH6) is simply a tool for separating powdery conidia from solid substrates such as grain, on an experimental scale. It has an upgraded motor & fan unit, but in all other ways the MycoHarvester 6 functions in the same way as the MH5 series: the cyclone has the same cyclone geometry to previous versions that have been in use since 2004. It has several potential applications, but its primary role to date has been in the formulation of promising microbial control agents (MCAs).
Many fungi produce hydrophilic (often slimy) propagules and the MycoHarvester is less suitable for these (although separation may still be possible if the conidiated substrate is made very dry).
To date, conidia of the following species are known to have been successfully separated from substrates using the MH 6 and used for biopesticide formulation or other processes:
It is impossible to exactly estimate yields for the wide range of isolates and substrates. The laboratory-scale MH 6 can help provide experimental information on future scale-up. It's primary objective is to aid the development of high quality formulations and thus enable "proof of concept" in trials of promising beneficial fungi. Reasonably-well surface dried substrate is typically processed in batches of approximately 1 kg, usually taking 1-4 minutes to process, so you might hope to process 10-12 kg in a working hour (in comparison, he MH3 unit can extract more than 0.5 tons substrate per day).
The efficiency of harvesting will likewise depend on the nature of the fungal isolate and the presentation of the substrate (especially its surface dryness). If the isolate is not very powdery, we recommend drying the substrate down to <20%. All these factors require experimentation, and we strongly recommend rigorous testing before scale-up production with the MH3 commences. For guidance only: existing MCA production systems typically convert grain substrate in the range of 25-150 g. conidia per Kg substrate. However, this can confuse the true screening requirements for potentially successful MCAs. If, for example, an isolate A yielded only 20 g/Kg, but was shown to be >10x more effective in the field than isolate B that yielded 100 g/Kg, it would still be much more cost effective to develop isolate A. The question of volume of product handled by operators can easily be adjusted at subsequent formulation stages.
How much do MycoHarvesters cost?
For prices click here. Researchers should actually ask themselves the question “Can I afford to test non-optimised MCA formulations?” Field trials are usually very expensive.
How can MycoHarvesters be upgraded as production needs increase?
Essentially the cyclones are standard units, but over the years, research groups have modified MycoHarvesters to suit the particular needs of various MCAs and production volumes. The latest upgrade has involve fitting a larger extraction fan for continuous use in small-scale production. Recent experience has shown that this can be more effort than it is worth, and more than one production facility has decided to have both an MH 6 - for pilot and experimental production - and a MH3 unit for "mainstream" extraction of >0.5 tons substrate / day. We have been cutting the costs of the latter, by providing matched cyclones and fan unit only, and giving detailed suggestions about local production of substrate handling units (which are bulky, heavy, but easy to construct). The internal geometry and airspeeds in the MH6 are very similar to those of the MH3, and we have carried out several comparisons to show that MCA particle spectra do not change substantially on scale-up.
What factors do I need to consider for installing MycoHarvesters?
Housing MH6 units is usually straightforward - they are bench-top units requiring less than 1 square metre of working space (but do consider working heights: substrate must be poured into a column at approximately 800 mm above the bench top). The separate motor and fan (connected via a tube) can be positioned well away from the cyclone and substrate column: for greater ease of operation and less noise in use. For extra safety, you might consider installing the substrat inlet under a dust hood. However, we understand that this is not always possible, so the machine is designed to suck-in any dust produced with the substrate and blow-out clean air (provided the spore cylinders are emptied regularly!). A large sink nearby for cleaning-out equipment is highly desirable. If possible, we recommend the use of a 220 v electrical supply, although there are 2 ways of working with 110 v, if absolutely necessary.
The MH3 only requires a medium-sized (e.g. 6 m x 5 m) room, but constitutes part of a large-scale mass production operation - a major issue is producing and warehousing all the substrate required. Easy access for processing substrate - and removal of spent substrate - will greatly improve operational efficiency. With a large fan extracting air from the cyclones, influx of clean air into the room must also be taken into account. Further advice on these matters is given with supply of equipment.
There are two aspects to safety considerations:
a. Electrical and electrostatic
The MH6 conforms
b. Inhalation and contamination
The MH6 creates a negative pressure at the substrate entry point, and effectively filters out all particles larger than 1µm, so the risks of releasing spores into the environment are considerably lower than methods such as sieving. This therefore provides a good "first line of defence" against inhalation of dust by the operator, but you are strongly advised to augment this with suitable personal protective equipment and to install the equipment in a suitable working zone away from other laboratory processes.
What happens to the contents of the second chamber and the spent substrate?
The contents of the second (larger particle) chamber often contain large numbers of spores and are usually re-cycled back with the following bag/batch of substrate.
The disposal of spent substrate requires more careful consideration. At least one commercial-scale operation considers the spent grain to be still useful as a source of inoculum and infectious to the target pest, applying "mycelial rice" as a form of granule to the base of the crop. More than one operation has composted the spent substrate – which has been converted into organic fertilisers.