Effects of compound microbial inoculants on the fermentation of fruit tree branches and the conversion efficiency of Protaetia brevitarsis larvae
Author of the article:DAI Li-Ming1** ZHANG Guang-Jie2, 3 CHEN Ai-Song1 DAI Fan-Shen1 Nuerguli·Nuermaimaiti1 LIU Yu-Sheng4*** MA De-Ying1***
Author's Workplace：1. Key Laboratory of Agricultural and Forest Pest Monitoring and Safety Control, College of Agriculture, Xinjiang Agricultural University, Urumqi 830052, China; 2. Engineering Research Center of Edible and Medicinal Fungi, Ministry of Education, Jilin Agricultural University, Changchun 130118, China; 3. Manas Golden Insect Biotechnology Co., Ltd., Changji 832205, China; 4. Xinjiang Mengli Agricultural Science and Technology Development Co., Ltd., Cele 848300, China
Key Words：Protaetia brevitarsis; compound microbial inoculant; larval conversion; fermentation duration; synergistic effect
Abstract：[Aim] To investigate the effects of different microbial inoculants on the fermentation of plant materials and on the breakdown of plant waste by Protaetia brevitarsis larvae, thereby improving the utilization of forest fruit waste [Methods] Single-, dual-, and triple-strain combinations were formulated. P. brevitarsis larvae were fed with plant material fermented for different durations (10, 15, 20 and 25 d). Using larval weight gain, feed intake, conversion rate, and other parameters as indicators, the optimal inoculant combination and fermentation time for a mixed fruit tree branch-cattle manure substrate were identified. [Results] Plant material that had been fermented for either 15 or 20 days was the most easily broken down by larvae. Although there was no significant difference between these fermentation durations, a comprehensive comparison indicated that the 20-day fermentation treatment was slightly better than the 15-day one. Among the 20-day fermented materials, the triple-strain combination (JD+YM+EM) outperformed all other inoculant treatments, achieving the highest fermentation temperatures and the best larval growth and development indicators. During the heating phase, the maximum temperature reached 68.9 °C, whereas during the thermophilic phase it peaked at 75.7 °C (remaining above 70 °C for more than three days), which was significantly higher than that of the single-strain (65.7-69.1 °C) and dual-strain combinations (67.3-70.4 °C). All inoculated treatments had better heating performance than the sterile control (58.8 °C). Larval feed intake ranked as follows: triple-strain combination (149.40 g) > dual-strain combinations (139.10-144.20 g) > single-strain combinations (129.00-133.70 g) > sterile control (129.50 g). Larval weight gain followed a similar order: triple-strain combination (14.70 g) > dual-strain combinations (10.10-13.30 g) > single-strain combinations (6.20-10.00 g) > sterile control (6.40 g). The optimal triple-strain combination achieved a larval biomass conversion rate of 80.06%, a feed utilization rate of 74.70% and a frass conversion rate of 97.26%. In conclusion, compared with single- and dual-strain combinations, the triple-strain combination had a significantly higher fermentation temperature, shorter fermentation period, and faster larval growth and development. [Conclusion] The triple-strain combination (JD+YM+EM) is the optimal inoculant formulation. Considering both production efficiency and cost, a fermentation period of 15-20 days is the optimal duration that balances effectiveness and efficiency under this system. This protocol markedly enhances the growth and development of P. brevitarsis larvae, and thereby provides a scientific basis for both the utilization of agricultural waste and insect protein production.