by Terry Green on 01/26/19
Since I last commented on the challenges of farming BSF larvae on a commercial scale back in 2016 (see Commercial Black Soldier Fly (BSF) Production in 2016 | Where Are We Today?) the number of companies and entrepreneurs interested in commercially farming BSF larvae steadily grown. Essential scientific research has also picked up regarding farming, propagation, and safety aspects of growing BSF larvae off varying substrate waste sources. There however are still a number of hurdles and challenges beyond those aired in my earlier comments needing attention. This is particularly apropos regarding current government regulatory guidelines designed to ensure the safety of “farmed insects” as an animal feedstock, or food product, and accompanying HACCP safety guidelines concerning oversight of the emerging industrial production of insects (see COMMISSION REGULATION (EU) 2017/893 and Hazard Analysis and Risk-Based Preventive Controls for Food for Animals - Guidance for Industry). This blog reviews some of these latter issues concerning the farming of BSF larvae on a commercial scale.
There is no question that entrepreneurs intending to commercially produce BSF larvae as an animal feedstock additive or food ingredient to be marketed to the public are duty bound to validate that their end products are safe and free of pathogens and toxins in meeting the same safety standards expected of any other producer of animal feed additives, or foods, marketed to the public. Food borne pathogens, including yeasts and molds, Bacilli and spore forming soil bacteria, have all been detected in harvested BSF larvae grown off of food waste, cooked rice, and calf forage, and in “feed grade” pet food (see The intestinal bacterial community in the food waste-reducing larvae of Hermetia illucens, Use of high hydrostatic pressure to inactivate natural contaminating microorganisms and inoculated E. coli O157:H7 on Hermetia illucens larvae and Safety aspects of the production of foods and food ingredients from insects). Enterobacteriacea and spore forming soil bacteria have likewise been found in dried meal worm (T. molitor) roasted at 55 C for 24 hours and held in storage (see Microbiological aspects of processing and storage of edible insects), underscoring the importance of having in place a rigorous HACCP protocol that addresses all aspects of an insect farming operation including the importance of protecting the end product against recontamination while in storage.
Propagating, growing, harvesting and preparing BSF larvae in a form suitable for incorporation into animal feedstock, or as a food product, on scientific, logistical and practical grounds, is however radically different from start to finished product from traditional methods of commercially processing animal feedstock additives and/or food products. Adult mating activity, the deposition of egg clutches in nutrient substrates needed to grow larvae, and larval burrowing and feeding off nutrient substrates, all occur under nonhygienic conditions.
Larvae cannot on practical grounds be grown under sterile conditions. They freely feed on and benefit from the presence of microorganisms growing in nutrient substrates housed in bioreactors throughout the first five instar (molting) stages of their life cycle where the possibility of competing potential pathogens growing off the same substrates fed to larvae cannot be entirely excluded.
The expectation that insects can be grown and harvested under hygienic conditions is incompatible with the fundamental environmental requirements needed in farming larvae. Larval propagation, their growth on nutrient substrates, and their harvest free of the substrate on which they have grown, all occur in an environment that is warm and humid, an environment typically maintained with a relative humidity of 50+% and with temperatures in the range of 25 to 40 C.
Consequently, HACCP guidelines in managing the production of insect products, in general, need to be designed so as to ensure that the end product, itself, is safe and devoid of food borne pathogens within regulatory guideline limits prescribed. It is simply not realistic to expect that the the processing train involved in farming insects overall can be maintained and operated under hygienic conditions.
Regarding government regulatory guidelines on allowable processes in farming insects, EU governmental regulations covering what is allowable and what is forbidden as a nutrient substrate were initially drafted to prevent and eradicate the threat of spreading transmissible spongiform encephalopathies (TSEs) in animal feedstocks of bovine, ovine and/or caprine origin (see Commission Regulation EU 2017/893 and Commission Regulation EC No 999/2001).
Currently these regulations specify that insects (including BSF larvae) can be fed nonruminant, but not ruminant, animal proteins, provided that the proteins and compounded feeds serving as larval feed substrate are produced and derived from slaughterhouses or cutting plants complying with EU regulatory guidelines drafted in 2001. The marketing of BSF larvae grown on substrates containing or contaminated with animal manures, ruminant proteins, catering (food scrap) waste, or meat and bone meal is specifically forbidden (see Articles 5 and 6, Commission Regulation EC 2017/893).
These EU regulatory guidelines in their present form hamstring the insect industry by banning the use of an inexpensive and abundant nutrient feedstock that otherwise could be used on a commercial scale in farming BSF larvae, namely catering waste, which if allowed under a set of revised guidelines could be used to substantially reduce the cost of farming insects.
Certainly manure, harboring pathogenic bacteria, viruses and parasites, unchecked, poses a significant health concern (see, for example, Pathogens in Manure, Pathogens and Organic Matter, and Human and Animal Pathogens in Manure). Accordingly, it makes sense to ban manures as an insect substrate under current regulatory guidelines. Banning catering waste as an insect feedstock in farming insects seems however unnecessary.
Why? Plain and simple, this is because (i) HACCP guidelines in monitoring the safety of farmed animals (insects included) are already in place and covered under EU and FDA regulatory guidelines; and (ii) because catering waste by virtue of having at one time already having met safety standards as a food product has already undergone and passed regulatory safety guidelines which require that foods for human consumption must pass through a higher safety standard than that of animal feed grade substrates already allowed under both EU and FDA regulatory guidelines.
The proposal for allowing the use of catering waste as a feedstock for farming insects in no way implies that catering waste at the time it is to be presented as a substrate feedstock to insects is still of food grade quality. It simply acknowledges the reality that safety guidelines in farming animals need in the end from a practical perspective to focus on the quality and safety of the end product produced providing the waste used is or was at one time food grade and free of contaminants which render it a high risk for the transmission of TSEs or other biohazards (vis., parasites, toxic heavy metals, herbicides, etc.).
Catering waste can be stored in a fermented state before it is fed to larvae wherein its pH drops to below pH 4 (see, for example, Soldier Fly Food Scrap Leachate | A Treasure Trove Amended in Soil, Amending Soil with Black Soldier Fly Processed Food Scrap Leachate and Using Black Soldier Fly Larvae for Processing Organic Leachates), a pH low enough to retard the propagation of pathogenic organisms in the waste (see, for example, Chapter 3. Factors that Influence Microbial Growth, Quantification of the Relative Effects of Temperature, pH, and Water Activity on Inactivation of Escherichia coli in Fermented Meat by Meta-Analysis and Parameters for Determining Inoculated Pack/Challenge Study Protocols).
Regarding the risk of cultivating and transmitting potential pathogens, it may be possible to also reduce the risk by exploiting the formation and accumulation of naturally occurring antimicrobial agents released from catering waste and larvae as larvae feed and grow off the latter waste through steady-state farming of larvae grown on catering waste (see Steady-State Farming of BSF Larvae). Melanin, for example, a potent antioxidant and broad spectrum antimicrobial agent (see Melanin properties at the different stages towards life cycle of the fly Hermetia illucens, The isolation, purification and analysis of the melanin pigment extracted from Armillaria mellea rhizomorphs, Exploring Antimicrobial Potentials of Melanin from A Black Yeast Strain, and Impact of Melanin on Microbial Virulence and Clinical Resistance to Antimicrobial Compounds), accumulates in catering waste processed by BSF farmed under steady-state conditions, in the chitinous exoskeleton of prepupae self-harvesting free of the waste, and in outer exoskeleton of adult flies (see Fig. 1).
Naturally occurring and potent broad spectrum antimicrobial peptides (AMPs) produced and isolated from the guts of BSF larvae might additionally be exploited in this regard in mitigating the cultivation of food borne pathogens in substrate processed in the larval bioreactors (see, for example, Comparative Evaluation of the Antimicrobial Activity of Different Antimicrobial Peptides against a Range of Pathogenic Bacteria and Scientific papers regarding black soldier fly larvae antimicrobial properties).
At this time little research has yet been done on exploring the possibility of exploiting the natural antimicrobial activities of either melanin, or larval AMPs produced by larvae growing off catering waste, in reducing the risk of cultivating food borne pathogens in decaying catering waste.
Fig. 1. Formation and accumulation of broad spectrum antimicrobial melanin in catering waste processed by BSF larvae under steady-state conditions (upper left image), the exoskeleton of prepupae harvesting free of the catering waste (upper right image), and the outer exoskeleton of adult flies (lower center image) (see also Melanin properties at the different stages towards life cycle of the fly Hermetia illucens, and Methods for producing melanin and inorganic fertilizer from fermentation leachates). © Copyright Terry Green, 2019.
Interestingly, Lelander et al. published observations in 2014, working with pig manure, demonstrating a 7 log reduction in spiked colony counts of Salmonella spp. and a sharp fall off in adeno-, reo- and enteroviruses while growing BSF larvae in a steady-state bioreactor. They also reported however that the drop off in spiked colony counts of Enteroccocus spp. and viable ova count of the parasite, Ascaris suum, was insignificant (see High waste-to-biomass conversion and efficient Salmonella spp. reduction using black soldier fly for waste recycling).
Substituting manure as a larval feed substrate in farming BSF larvae in place of catering waste unfortunately poses many more challenges concerning the safety of the end product, not only with regard to the risk associated with the introduction of parasites infesting manure into the end product, but also because of the risk of contaminating larvae grown off manure substrates with high inoculums of pathogenic Enteroccus spp. commonly found in manure. In the study by Lelander et al., the use of manure as a larval feed substrate, and their finding of only moderate declines in colony counts associated with Enteroccus spp. could, in light of the source of the waste used for growing larvae in their experiments, be attributable to simply cycling and re-inoculating Enteroccus spp. back into the substrate residues they analyzed.
Concerning another challenge needing more attention in farming BSF larvae, it is important to consider the matter of end product safety relative to the presence of naturally occurring fungi. Spore forming fungi of soil and plant origin are ubiquitous in Nature, they are present on the surfaces of all plants including food grade vegetables and fruits, spices and various grains, and in the spore form are generally regarded as posing no food safety hazard. The diversity of microbiota isolated from the gut of BSF larvae growing on different feed substrates however varies widely and has been found to be most diverse with larvae fed catering wastes (see, for example, A survey of the mycobiota associated with larvae of the black soldier fly (Hermetia illucens) reared for feed production). This includes fungi, some of which are capable of producing mycotoxins, the latter byproducts considered however unacceptable in feed grade products regulated by the EU (see Mycotoxins).
Bosch et al. in 2017, looking at the risk of mycotoxin carryover in harvested BSF and meal worm larvae, based on their findings reported however that in the case of these two larval species grown on plant waste feedstocks contaminated with and/or spiked with toxic concentrations of aflatoxins, that they do not appear to accumulate or harbor mycotoxins (see Black Soldier Fly Larvae (Hermetia illucens) and Yellow Mealworms (Tenebrio molitor)). They surmised that these two larvae species tested either have the capability of excreting and/or catabolizing mycotoxins, but they left open the possibility that the larvae could also sequester the toxins in a form no longer detectable by standard screening protocols.
A sharp drop in aflatoxin levels in the residue substrate at the end of their experiments was however also evident. This might suggest that the aflatoxins spiked in the feedstock substrates may also have undergone degradation either by microbes growing in the substrates and/or by enzymes commonly present in the residual substrates left behind in their bioreactors (see Mycotoxin Biotransformation by Native and Commercial Enzymes: Present and Future Perspectives).
Several useful detailed and practical reference sources are available in helping entrepreneurs contemplating how to begin setting up a HACCP food safety plan in farming BSF larvae on a commercial scale (taking however into account some of the caveats noted in this blog concerning differences in farming BSF larvae relative to other food processing technologies) can be found on the internet (see, for example, Validating the Reduction of Salmonella and Other Pathogens in Heat Processed Low-Moisture Foods, Draft Guidance for Industry: Hazard Analysis and Risk-Based Preventive Controls for Human Food, Draft Guidance for Industry: Hazard Analysis and Risk-Based Preventive Controls for Human Food - Appendix 3 Bacterial Pathogen Growth and Inactivation and Safety aspects of the production of foods and food ingredients from insects).
Rapid screening techniques are available which can be helpful in helping monitor the safety of the end product (see, for example, Prevalence and Methodologies for Detection, Characterization and Subtyping of Listeria monocytogenes and L. ivanovii in Foods and Environmental Sources, Fast & Reliable Salmonella Test Kits, RapidChek® Listeria monocytogenes, Listeria Environmental Listeria species Test , MicroSnap | E. coli, 3M™ Petrifilm™ Plates, etc.). It is important to realize that some of these in-house commercial “rapid screening” methods may however not be reliable because of interferring substances in the test matrix leading to false negative or false positive test result. This is particularly true regarding misinterpretation of test results associated with differential biochemical agar plate and/or color indicating technologies.
The technological evolution of the insect farming industry overall still faces some formidable hurdles in achieving economic viability, particularly regarding large scale commercial farming of BSF larvae as an animal feedstock additive or food product. Nevertheless, providing an HACCP safety plan is put in place which focuses on the important critical control points needing to be addressed to ensure a safe end product, and followed, the goal of producing safe end products in compliance with government regulatory guidelines should be achievable.
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