On the Compositional Analysis and Biorefinery of the Black Soldier Fly (Hermetia illucens) – Resolving Uncertainties & Towards More Sustainable Processing

The continuously growing world population alongside our higher standard of living and the accompanying increased demand for resources and waste production, put an enormous pressure on our planet. Though, the larvae of the black soldier fly (Hermetia illucens, BSF) are more than qualified to deal with municipal waste, while simultaneously contributing to the demand for resources. During their fast rearing cycle, they efficiently convert low-value, organic waste streams (i.e., supermarket waste, restaurant waste) into high-value and renewable biomass rich in lipids, lauric acid, proteins, and chitin. For this reason, BSF larvae are an excellent candidate to serve as sustainable and renewable feedstock in a circular bioeconomy where petroleum is displaced by biomass as primary source of energy and materials. It goes without saying that suitable and accurate analysis procedures are required to determine the quantity of these compounds in the larvae. Through the so-called biorefinery, these compounds can then be recovered or extracted from the larval biomass to serve as industrial feedstock for the production of detergents and cosmetics, among others. Yet, important uncertainties and knowledge gaps were present regarding these analysis procedures and the biorefinery, which were resolved in this dissertation. In addition, the first initiative at making the biorefinery more sustainable, without compromising the extraction efficiency or purity of the extracted compounds, was taken as well. In the first part, the suitability of a biorefinery procedure using acids, bases, and solvents for multiple BSF life stages (i.e., larvae, prepupae, pupae) was investigated. This is highly relevant considering these three life stages occur together during the same rearing batch. Despite some differences in the composition of the extracts, the procedure was deemed suitable for all three life stages. It was, however, deemed relevant to time the harvest accordingly, depending on the desired application of the extracts. For instance, later life stages were characterised by higher chitin and lauric acid contents. An alternative for the gravimetric chitin analysis was investigated as well, considering such procedure is not able to differentiate chitin from other fibres like cellulose. Instead, a procedure was developed in which chitin was first hydrolysed and deacetylated into glucosamine before quantifying the latter by means of liquid chromatography. The optimised procedure was not only much faster than the gravimetric procedure, it was also characterised by a high specificity, accuracy, and precision. Another uncertainty which was resolved in this dissertation, is whether the results of two frequently used, though inherently different, analysis procedures (i.e., Kjeldahl and Dumas) are interchangeable for determining the nitrogen content of BSF larvae. Following this investigation, for which a large variety of larvae was used, it was found that the results are indeed interchangeable. A more robust nitrogen-to-protein conversion factor was determined as well, which allowed for a more accurate calculation of the protein content of BSF larvae. By combining all results, insight into the nitrogen distribution of the larvae was gained as well. In the final part of this dissertation, the green and biomass-derived solvent 2-methyltetrahydrofuran (2-MeTHF) was evaluated as alternative for hexane to extract the lipids. Through Design of Experiments, an extraction of fresh larval biomass was optimised as well, in order to assess whether a costly and energy intensive drying step preceding the lipid extraction could be omitted. It was found that 2-MeTHF was able to extract a higher amount of lipids from dry biomass compared to hexane. Furthermore, the optimised extraction with 2-MeTHF from fresh biomass performed similar to the extraction with hexane from dry biomass. The composition of the extracts was highly similar, highlighting the potential of the extraction with 2-MeTHF from fresh biomass as alternative for the extraction with hexane from dried larval biomass.

Jaar van publicatie:2021

Toegankelijkheid:Open