At the Miaoli District Agricultural Research and Extension Station (MDARES) of the Council of Agriculture, staff pull up a thick black curtain, and place male and female silk moths one after another into their “bridal chambers.” The “moth dust” (actually tiny scales) that flies about the room eventually settles. This is the task of breeding a new generation of silkworms, which the MDARES undertakes every spring and autumn. At present they are conserving 136 breeding lines of the domestic silk moth (Bombyx mori).

Although silkworm rearing was already in decline in Taiwan by the 1980s, with the development of biotechnology it was found that natural silk can be used as a raw material for high-end biomedical products. Moreover, the silkworm pupae (a.k.a. chrysalises), which for silk farmers were merely waste, are in fact a source of high-protein nutrition and can be repurposed into functional pet food.

Workers help male and female silk moths of the same breed to mate in order to preserve their genetic lineage.

The treasure inside the cocoon

Liao Chiu-hsun, an assistant researcher in the Sericulture and Apiculture Division at MDARES, notes that in the face of a global food crisis, insect protein is one option to replace animal protein. Silkworm pupae are a source of high-protein nutrition, and in Korea canned silkworm pupae are eaten as a side dish when drinking, while in Thailand they are a snack food.

But in Taiwan, silk farmers have always simply discarded silkworm pupae, keeping only the cocoons; at most the pupae have been composted.

Liao Chiu-hsun, who has been studying silk moths and silkworms (the silk moth larvae) for more than a decade, notes that when silkworms sense danger, they instinctively activate a special immune mechanism through which they secrete a kind of antimicrobial peptide that wards off attacks by invasive micro­organisms. Feeding tests on broiler chickens and mice have shown that this peptide can suppress the reproduction of harmful Escherichia coli and Clostridium perfringens bacteria, thereby reducing the propagation of harmful bacteria in the intestinal tract. When added to animal feed, the peptide can have an effect analagous to antibiotics, promoting animal health.

Using their own silk moth germplasm bank, the MDARES crossbred four silk moth strains and selected a variety that they named ‘Guofu Nongfeng’ for promotion to silk farmers. The silkworms are fed on Taisang No. 2 and Taisang No. 3 mulberry leaves, which are tender and fragrant and stimulate the silkworms’ appetite. As a result a Guofu Nongfeng silkworm can grow to weigh up to 5.5 grams, which is double the weight of other silkworms. They also produce a larger cocoon of silk, weighing 0.3 to 0.5 grams each.

Silkwork pupae, hitherto regarded as waste by silk farmers, are in fact a source of high-protein nutrition.

Sustainable tastiness

Because the silkworms can only eat organic mulberry leaves, their pupae are an excellent source of animal protein for sustainable circular agriculture. Therefore in 2018 the MDARES, in coordination with the Council of Agriculture’s Program for Animal Health Technology, began investigating the feasibility of using silkworm pupae as an additive in pet foods and animal feeds. They completed their research and transferred the tech­nology to the private sector in 2021.

Eva Liu, a manager at Furtime Pet Food Company, which is the recipient of the technology transfer, says that when they first put out canned cat food made with silkworm pupae, pet owners worried that they would see insect corpses in the cans. However, she explains that the appearance of this kind of cat chow is no different from ordinary cat food. When Furtime began raising capital, they reached 630% of their initial target, and in the year since the product has been on the market sales have tripled.

Silkworm pupae are mainly used as a health ingredient in canned cat food. In order to make this ingredient more acceptable to notoriously finicky cats, R&D staff have had to put a lot of effort into devising the right recipes. For example, they have added in essence of chicken and essence of milkfish to make the food more fragrant so that cats, who are heavily scent-­oriented, will find it appetizing.

Furtime researcher Eric Peng says that in the UK people are already using protein from insects like the black soldier fly to make dry cat and dog foods, but he believes Taiwan is the first place in the world where canned cat food is made using silkworm pupae. He expects healthy functional pet foods such as those that include probiotics or silkworm pupae to become increasingly popular with cat lovers.

Mung bean hulls, soybean residue, and coffee grounds have all been seen as agricultural “waste” products. But thanks to technology, they can be transformed into functional animal feeds, and can even be turned into new plant-based antiviral medicines.

Freeze-drying technology can be used to turn ingredients including silkworm pupae and fish into the dry condiment furikake.

Functional food made with silkworm pupae is suitable for cats, who are not big eaters.(photo by Kent Chuang)

From the dregs

In 2008 Hugo Yang, founder of King’s Ground Biotech Company (KGbio), located in Pingtung County, began two years of work to find the most suitable bacteria for solid-state fermentation from among more than 40 bacterial strains. From there, his firm developed an animal feed additive that can inhibit viral infections and viral replication in animal cells and so enhance the health of farm livestock.

According to the Compendium of Materia Medica, compiled by Ming-Dynasty medical expert Li Shizhen (1518–1593), mung bean acts as a diuretic and detoxicant and can reduce swelling. But for ­modern ­production one must first confirm the active ingredients in the laboratory, and develop production processes to extract these ingredients in stable form and predictable quantities. To achieve this, Yang recounts, in the first year KGbio scrapped its newly built solid-state fermentation system and rebuilt it to a new design at a cost of NT$40 million. They finally produced a reddish-brown powder for use as an additive in functional animal feeds. Through testing on cells and in animals, they collected persuasive data of the product’s effectiveness and in 2010 launched it onto the market under the name of “Viva.” 

Hugo Yang, founder of King’s Ground Biotech, says that agricultural byproducts like soybean residue and mung bean hulls can become new materials for high-value-added applications in the circular economy.

Well-known in export markets

Beebee Pi, associate dean of the company’s R&D Department, says that after fermentation the mung bean hulls undergo a process to extract “phyto­genics”—plant-derived natural growth promoters. The active ingredients have a chemical structure similar to that of estrogen. The oviducts of layer hens are prone to inflammation, and field tests show that the Viva feed additive strengthens the hens’ immune systems and boosts their laying rate.

KGbio began exploring export markets and in 2018 won its first order from Charoen Pokphand Foods of Thailand, the world’s largest animal feed producer. KGbio has since developed markets in Vietnam, Malaysia, and the Philippines, and in 2021 began selling its products in Korea and Japan. In 2021 exports accounted for nearly 70% of total operating revenues.

Yang says that during the outbreak of avian influenza in the US last year, which led to a shortage of chicken meat, Viva—which received a patent in 2020 based its on properties in inhibiting influenza viruses, including avian flu—came into its own. As KGbio’s claims were backed up by data from academic studies, the main difficulty in promoting Viva turned out to be that Americans had never heard of fermented mung beans, so salespeople had to spend a lot of time explaining the product to them.

Sustainable raw materials

Besides mung bean hulls, solid-state fermentation of coffee grounds can also yield an extract that can be used an animal feed additive. Academic research confirms that this additive has an antibacterial effect that benefits the respiratory health of livestock, and the company is currently applying for a patent. Yang says that from the perspectives of precision nutrition and preventive medicine, healthy plant-based feeds that increase animal survival rates can become a third pillar of animal health alongside medicines and vaccines.

At present there is a serious global shortfall of protein sources, and Taiwan relies on imports for more than 90% of its raw materials for animal feed.

Taking soybean residue as an example, solid-state fermentation transforms soy powder into small proteins, making it easier to digest. It can be used to make a feed that is flavored with dried fish floss, to replace animal protein. For pigs, which prefer sour and sweet flavors, this feed is a gustatory delight and an excellent source of protein.

Yang says forcefully: “To us, agricultural byproducts like soybean residue and mung bean hulls are not waste, but are new materials with high-value applications in the circular economy. They are also optimal solutions in response to the Big Granary Project that the government is currently promoting.”

King’s Ground Biotech’s core R&D competence has enabled them to turn agricultural byproducts into raw materials for functional animal feeds.

A model of the circular economy

When Yang speaks of “high-value applications,” he is referring to the fact that one kilogram of soybean residue costing NT$0.2 can, after being turned into a raw material for functional feeds, be worth 100 times as much.

KGbio’s first factory, which has annual revenues of over NT$100 million, can only handle 1,200 metric tons of agricultural byproducts each year. To expand its production capacity, the company broke ground on their second factory on June 6, 2022, and once the plant is completed at the end of this year the firm expects to be able to process 6,000 tons of raw materials per year.

KGbio calculates that it has invested NT$180 million in R&D on mung bean hulls over the last 16 years. Beebee Pi reveals that fully half of the company’s employees (including production workers) have master’s or doctoral degrees. With R&D as its core strength, KGbio was able to cooperate with National Taiwan University to confirm the antiviral properties of mung bean extract. These research results have not only been published in the medical journal Frontiers in Pharmacology, they have enabled the product to be patented in Taiwan and patent applications are currently pending in the US and Japan.

As Hugo Yang says: “We use technology to get to the heart of the earth’s waste, and employ an innovative commercial model to manifest the value of living things.” This is also the real meaning of the circular economy—not only do enterprises make profits, but the planet can be sustainable as well. 

Feeding animals with functional animal feeds using extracts from fermented mung bean hulls, soybean residue, and coffee grounds is similar to the concept of people taking multivitamins.