Methods for producing melanin and inorganic fertilizer from fermentation leachates

Abstract

Melanin or inorganic fertilizers are produced from fermentation leachates or from low-cost nutrient-rich solutions. The method for producing the melanin or inorganic fertilizer comprises repetitive trophic cycling in the controlled conditions of primary and secondary bioreactors. Nutrients are cycled between microorganisms such as bacteria, yeast and fungi and black soldier fly larvae, Hermetia illucens. Polysaccharides are partly converted into natural melanins or inorganic fertilizer, which are difficult to biodegrade and hence accumulate in the bioreactors. The method can employ, as a source of nutrients, leachates produced from food waste or from sugar-rich liquid waste of the food industry. These leachates can be used raw or can be augmented with low-cost sugar-rich solutions such as molasses, hydrolyzed cellulose or starch. The method is inexpensive and does not require the use of expensive chemically-defined culture media.

Description

1. TECHNICAL FIELD[0001]The present invention relates to methods for producing melanin, melanin-associated proteins and inorganic fertilizer from fermentation leachates or from nutrient rich solutions spiked with low cost, sugar-rich sources.2. BACKGROUND OF THE INVENTION[0002]Melanin is one of a very few examples of natural organic semiconductors and was demonstrated to be such in the early 1970s. Melanin is thus a desirable natural, environmentally friendly material with many known applications for the electronics industry. Melanin can be used to produce a wide variety of biologically friendly electronic devices and batteries used in applications such as medical sensors and tissue stimulation treatments.[0003]Many metazoans and microorganisms form melanin naturally. Because the concentration of melanin in these organisms is generally low and melanin is very insoluble, melanin extraction is inefficient and natural melanin is expensive. It is known in the art that the yield of melan...

AI Technical Summary

Problems solved by technology

The exception is polyphenols (such as melanins), which cannot be digested by the larvae or easily decomposed by microbial activity, and consequently accumulate in the medium.

Not all sources, however, are appropriate for high melanin yield.

Vegetal wastes that are very rich in cellulose but poor in sugars and starch (such as hay, straw or corn stover), can be used, but are of lesser value because they do not decompose fast enough in the primary bioreactor (FIG. 3).

Animal carcasses, bones, skins, entrails, oils, grease and dairy products aggravate management, odor and pest problems, and greatly increase health risks due to food-borne pathogens such as Salmonella, Listeria, E. coli and Campylobacter (to name only a few).

Sewage liquid and sludge are not recommended as feedstock because they are also a health hazard.

They are also inefficient in the production of melanin because they are eaten by both microorganisms and BSFL, and because they do not stunt the growth of the larvae.

Manure, used in excess, increases the risk of spreading coliforms and other pathogens (especially if the larvae produced in this process are to be later used as feedstock for animals).

BSFL that are fed excessively with animal-derived products mature fast but are sloppy eaters and food-selective.

This will result in excessive animal decay odor and creates health risk problems.

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