Rearing of silkworm larva in a closed gas revitalizing plant system

Plant growing and insect breeding experiments in the CICS (Closed Integrative Cultivating System) were carried out. The CICS was established for collecting experimental data to investigate gas circulation and mass exchange between plants and animals as well as animal growth and nutrient compositions in the Bioregenerative Life Support System. The CICS was 1.4 m high with the base measuring 1.4 m × 0.8 m. In the plant chamber, stem lettuce plants were grown in a staggered manner. Silkworms in five different instars were fed in the animal chamber. Every 4 days, the silkworms that had been in the 5th instar for 3 days and all the silkworm’ excreta were taken out of the system. Meanwhile, the silkworms in the first instar were transferred into the animal chamber. During this process, O2 and CO2 concentrations in the CICS were measured, and the growth and nutrient composition of the silkworms in the system were compared with those of silkworms reared in the open environment. Results showed that O2 and CO2 concentrations in the system were 19.07–20.61% and 0.11–0.35%, respectively. The comparison of growing differences between the silkworms fed in the animal chamber and those in the open environment indicates the insect's biomass increasing rates and bioconversion rates in the CICS were lower than those in the open environment, and the amounts of excreta produced in the animal chamber were larger. Protein content of the SP (Silkworm Powder) produced in the CICS was more than that in the open environment, while fat content of the SP in the CICS was lower than that in the open environment. Calcium, phosphorus and iron contents of the SP produced in the CICS were 139.00 mg calcium/100 g SP, 1.20 mg phosphorous/100 g SP, and 7.95 mg iron/100 g SP. In terms of amino acids, the quality of the SP produced in the CICS was equivalent to that gained in the open environment.

Research highlights► Establish a Closed Integrative Cultivating System to investigate gas exchange between silkworms and lettuce, the nutrients and growth of silkworms and so on; such a manmade system can be used in the Bioregenerative Life Support System which provides daily necessities for the astronauts during the deep space exploration process and for people living in the extreme environments including desert, isolated military facilities including warships and submarine, north and south poles and so on for ecological engineering. ► Provide a way for engineers in the fields of contaminant transfer, ecological balance and so on to study the mass transfer in the ecosystem containing different biological creatures. ► Propose a new method of providing animal protein with high quality by feeding silkworms with inedible biomass of stem lettuce which can be utilized in the construction of recycling agriculture.