So it has been a few weeks since my last blog post and for that- my apologies. Travel and holidays slowed my reading down and consequently my writing.
The good news is my year is slowing down a bit as I am on my next to last trip for the year and then a brief reprieve with family during the Christmas holiday (lots of time to write during holiday). Other good news is I have a number of papers recently published to review and hopefully share with you as well.
The paper for today's post is pretty cool as it provides a comprehensive assessment of the microbiome associated with different waste streams, facilities, and scales (laboratory and industrial).
Wynants, E., L. Frooninckx, S. Crauwels, C. Verreth, J. De Smet, C. Sandrock, J. Wohlfahrt, J. Van Schelt, S. Depraetere, B. Lievens, S. Van Miert, J. Claes, and L. Van Campenhout. 2018. Assessing the microbiota of black soldier fly larvae (Hermetia illucens) reared on organic waste streams on four different locations at laboratory and large scale. Microbial Ecology.
Before I review the study and its finding, I would like to spend a few seconds discussing the importance of the microbiome (check out this page as related to the human microbiome). For those that do not fully understand the microbiome, it is the community of microbiomes inhabiting a given environment. This community often is described to include bacteria, fungi, protists, viruses, and more. With the work currently being done, most has focused on bacteria and fungi. Research is finding the microbiome is extremely important regulating physiology and behaviors of their hosts- something very cool (check out paper on interkingdom communication [in this case, interactions between microbiomes as well as their interactions multicellular organisms).
Characterization of these species is highly dependent on global efforts to describe them all (molecular methods) and store these data in data bases for others to use. Needless to say, even with given technology, we are just scratching the surfaces in terms of identifying and describing the host of microscopic organisms found in practically all habitats around the world.
Now - back to the study and what they did... and what they found.
The study explored the microbiome associated with different waste streams from different companies. They determined the microbiome of larvae as well as the remaining wastes after digestion.
The big picture determined there is tremendous variability across batches within sites as well as across sites. They also determined some pathogens were detected (e.g., Salmonella); however, the origins of these pathogens was not clear. The researchers also determined the microbiome was quite different in the larvae than the substrates on which they feed. This discovery is to be expected as the BSF larvae, like many other saprophytic species cultivate the microbiome associated with a resource as a means to suppress pathogens as well as create an environment appropriate for their maximal use of the resource.
Takeaway: More work is sorely needed exploring the microbiome for safety and production reasons.
As a FYI- these authors published another paper on this topic which was reviewed in the blog back in May 2018.
De Smet, J., E. Wynants, P. Cos, and L. Van Campenhout. 2018. Microbial community dynamics during rearing of Black soldier fly larvae (Hermetia illucens) and impact on exploitation potential. Applied Environmental Microbiology 84.
Jeffery K. Tomberlin, PhD, Lover of all things great and small (reference to microbes)
I will not spend a lot of time going into details on this publication with my colleagues Moritz Gold and Alexander Mathys at ETH in Switzerland, and Stefan Diener, Christian Zurbrügg with EAWAG because the paper is open access (yes!! many thanks, Alex!). I am really excited about the details provided here. And, I think you will enjoy the read as well.
Gold, M., J. K. Tomberlin, S. Diener, C. Zurbrügg, and A. Mathys. 2018. Decomposition of biowaste macronutrients, microbes, and chemicals in black soldier fly larval treatment: A review. Waste Management 82: 302-318.
One final note- congrats, Moritz on a great paper. Very impressive to witness a PhD student lead such a massive effort to produce such a quality product. Well done!
Jeffery K. Tomberlin, PhD, Paper Publisher!
One thing I always enjoy is reading papers published by graduate students. The paper to be discussed today is by Zhongyi Liu (Jay) and his colleagues out of New Zealand. I had a chance to communicate with Jay a few times over the past year or so. And, I truly appreciate his enthusiasm for working with the BSF. I am not sure if this is his first paper or not- but congrats, Jay! Job well done. I am glad this paper came across my desk today.
The study is a straight forward life-history study of the BSF when grown on three waste streams. Two wastes are common in such studies (e.g., brewery waste and pig manure), while the third I believe is fairly unique (e.g., semi digested grass). The publication information is:
Liu, Z., M. Minor, P. C. H. Morel, and A. J. Najar-Rodriguez. 2018. Bioconversion of three organic wastes by black soldier fly (Diptera: Stratiomyidae) larvae. Environmental Entomology.
The treatment of most interest to me was the "semi digested grass". This material was not defined in the manuscript (based on my reading- apologies if I missed it) so I am not sure of its composition or how it was produced. I looked up the supplier, and it appears to be a producer of free range lambs.
The development of BSF was compared across these treatments as well as a the semi digested (e.g., broll- wheat bran and wheat flour). I have to admit, broll is a new term for me. Based on information in the study, and new to me, this material is fed to chickens as a feed. This material is the standard for producing BSF used in the primary lab affiliated with this study.
Basic parameters of BSF growth were measured, including survival, development time, larval weight gain, development rate (weight/time), and prepupal dry weight. There were definitely treatment effects- especially for the semi digested grass (massive amounts of time to develop- 70 d vs 14/17 d on other treatments). Other measures were significantly lower for grass-fed larvae (interesting term use as most recognize its use with livestock production) including prepupal weight being 50-75% less.
Other factors measured included protein and fat content- this result is interesting as the protein content was comparable across treatments (40-50%), while fat was significantly lower for those reared on the semi digested grass (5% rather than 17% or greater). The fat content in the manure-reared prepupae was low (based on my experiences) at 17%.
The authors also did a meta-analysis across studies- something I will not dive into here; but, a topic you might consider reviewing to gain perspective across studies.
The authors conclude the semi digested grass is not a suitable resource for producing BSF. However, I would encourage some restraint in closing the door on such opportunities. My reasoning being, 1) it worked (just not to the level produced for other resources), and 2) with what we are learning about the microbiome, I suspect there are steps that can be taken that will allow for enhancements in the system to allow more optimal production levels.
Jeffery K. Tomberlin, PhD, Supporter of Graduate Researchers
I came across this paper today while surfing the web for new information on the BSF. I have to admit, I hadn't thought about pathogens being associated with seaweed; but, I understand the concern. Especially if someone is considering the mass-production of BSF from such material. In the end, we should all recognize that such assessments need to be made on all potential feed streams for the BSF. Here is the link for the paper, but I am not sure you will be able to access the full publication or not. Just in case, I have provided a summary below.
Swinscoe, I., D. M. Oliver, A. S. Gilburn, B. Lunestad, E.-J. Lock, R. Ørnsrud, and R. S. Quilliam. Seaweed-fed black soldier fly (Hermetia illucens) larvae as feed for salmon aquaculture: assessing the risks of pathogen transfer. Journal of Insects as Food and Feed 0: 1-14.
In this case, seaweed, many types are harvested from the wild or cultivated for use as livestock feed. Based on the introduction of this paper, seaweed can be surface colonized by a variety of human and fish pathogens- namely, E. coli and Listeria spp (examples of fecal indicator organisms [FIO]).
Findings in the study were fairly promising:
1- FIOs were at low levels in the larvae at the time they were harvested from the seaweed.
2-Larval meal and extracted lipids were free of FIOs
3-Handling larval meal and other associated activities resulted in contamination- but processing treatments decontaminated the insect-meal.
Questions to ponder:
1-What was the microbial load of the BSF used in the experiment at the time of initiation?
2-What is the shelf life of the finished product?
3-Can methods be employed to remove concerns about potential contamination after production (e.g., e-beam technology)? And, if so, is it economical and would it extend shelf life of the product?
Jeffery K. Tomberlin, PhD, Supportive of Developing SeaLarvae!
Individuals with over 25 years research experience with the black soldier fly. We are passionate about the science behind the black soldier fly and its ability to convert waste to protein.
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