Black soldier fly larvae (BSFL) convert kitchen waste into high-quality insect feed. However, the optimal amount of auxiliary materials needed to improve the physical and chemical properties of kitchen waste and enhance BSFL bioconversion efficiency remains unresolved. In this study, maize stover and BSFL frass were added to kitchen waste (in groups G2 and G3, respectively) to explore their effects on the growth performance and bioconversion efficiency of BSFL. The group with only kitchen waste, without the addition of maize stover or BSF frass, was used as the control group and labeled as G1. On the 5th day, the body length of the BSFL in the G2 group was significantly greater than that in G1 and G3 (p < 0.05). The dry matter weight loss rate in the G3 group was significantly lower compared to that of G1 and G2 (p < 0.05), and the feed conversion rate (FCR) of G1 was significantly lower than that of G2 and G3 (p < 0.01). In summary, adding maize stover and BSFL frass increased BSFL feed intake and improved body weight gain. However, these additives did not significantly enhance BSFL bioconversion efficiency. The organic matter in maize stover and BSFL frass was utilized by the BSFL, and the heavy metal levels in each group of BSFL did not exceed standard limits.

In this study, a novel strain exhibiting heterotrophic nitrification was screened; subsequently, the strain was identified as Klebsiella pneumoniae LCU1 using 16S rRNA gene sequencing. The aim of the study was to investigate the effects of external factors on the NH₄⁺-N removal efficiency of strain LCU1 in order to elucidate the optimal conditions for NH₄⁺-N removal by the strain and improve the removal efficiency. The findings indicated that the NH₄⁺-N removal efficiency of the strain exceeded 80% under optimal conditions (sodium succinate carbon source, C/N ratio of 10, initial pH of 8.0, temperature of 30 °C, and speed of 180 rpm). The genome analysis of strain LCU1 showed that key genes involved in nitrogen metabolism, including narGHI, nirB, nxrAB, and nasAB, were successfully annotated; hao and amo were absent, but the nitrogen properties analysis determined that the strain had a heterotrophic nitrification ability. After 120 h, the NH₄⁺-N removal efficiency of strain LCU1 was 34.5% at a high NH₄⁺-N concentration of 2000 mg/L. More importantly, the NH₄⁺-N removal efficiency of this strain was above 34.13% at higher Cu²⁺, Mn²⁺, and Zn²⁺ ion concentrations. Furthermore, strain LCU1 had the highest NH₄⁺-N removal efficiency of 34.51% for unsterilised (LCU1-OC) aquaculture wastewater. This suggests that with intensive colonisation treatment, the strain has promising application potential in real wastewater treatment.