The effect of Rhodococcus rhodochrous supplementation on black soldier fly (Diptera: Stratiomyidae) development, nutrition, and waste conversion

Abstract

Black soldier fly larvae are mass produced globally for use as livestock, poultry, and aquaculture feed. Efforts are continuously seeking processes optimising larval rate of growth, size, and waste conversion as a means to lower cost and increase output. Manipulating microbes in the larval substrate (i.e. fermentation or supplementation) has been demonstrated as a potential solution. However, identifying appropriate microbes for use in this process has been limited. The objective of this study was to determine whether supplementing black soldier fly larvae with the oleaginous microbe Rhodococcus rhodochrous would result in accelerated larval development, increased final larval body size, and increased conversion efficiency. Larvae fed a sterile, or non-sterile, diet treated with R. rhodochrous grew 3× faster than the control by the third day and were approximately 2× larger than the control by the conclusion of the experiment. Conversion rate was 2× greater for the treatments indicating less feed would be needed to achieve maximum weight gain. Protein composition of resulting larvae fed diet supplemented with R. rhodochrous, was significantly different than the control not receiving the microbial infusion. Larvae provided the microbe had 4.20 and 2.79% greater fatty acid composition and short-chained fatty acids, respectively, but lower monounsaturated fatty acids (1.60%) and polyunsaturated fatty acids (2.4%). Furthermore, larvae provided R. rhodochrous produced significantly more proteins related to energy production and storage, as well as muscle development and contraction, while those sans microbe, produced proteins related to stress responses (e.g. heat shock proteins). While, this study yielded positive results for the inclusion of R. rhodochrous as part of the black soldier fly larval diet, additional research is needed to optimise the dose at an industrial scale.

Dynamic changes in species richness and community diversity of symbiotic bacteria in five reproductive morphs of cotton aphid Aphis gossypii Glover (Hemiptera: Aphididae)

“…gossypii and the detoxification of toxic plant substances ( Gao et al, 2022 ). However, whether the P450 monooxygenase in Rhodococcus directly affects the metabolism of aphids is not clear ( Franks et al, 2021 ) have found that diet treatment with Rhodococcus can raise diet conversion efficiency, thus increasing body size in black soldier fly larvae. Based on these findings, we hypothesized that Rhodococcus in cotton aphid might be also responsible for biotransformation and biosynthesis.…”

The Use of Probiotics during Rearing of Hermetia illucens: Potential, Caveats, and Knowledge Gaps

“…All strains exhibited cellulolytic activity tested on CMC plates. Next, oleaginous microbes, for instance Rhodococcus rhodochrous , have been opted to be of probiotic value due to their high fat content and versatile metabolism [ 40 , 41 ].…”

“…1069/2009 [ 56 ]. Interestingly, feeding substrates were autoclaved in a few studies [ 41 , 43 , 47 ], probably to support colonization of the probiotics in the diets as this method would limit competition with other microorganisms. Yet, these sterilized substrates also resulted in a slower development of BSFL [ 23 , 47 , 57 ].…”

“…There is a great difference between the larval ages at the moment of supplementation ( Table 1 ). For instance, Kooienga et al [ 40 ] and Franks et al [ 41 ] started their experiments with 11 day-old larvae, whereas in the study of Li et al [ 43 ], sterile food waste was inoculated individually with six bacterial strains and served as feed for larvae directly after hatching to ascertain early colonization. Neonates might not have a fully developed microbiota [ 27 ], so it can be postulated that alteration of the microbiota is more feasible in younger larvae.…”

“…In the class of Actinomycetia, the oleaginous microbes Rhodococcus rhodochrous and Arthrobacter sp., have been tested. At a bench scale, daily feed supplementation with a fat-rich Rhodococcus rhodochrous strain to the (autoclaved) Gainesville diet resulted in higher waste conversion rates, a near doubling in larval weight and differences in fatty acid composition and protein expression profiles [ 41 ]. Moreover, the daily supplementation of an Arthrobacter strain to 300 larvae resulted in higher larval weight and lower waste:larva ratio [ 40 ].…”