Black soldier fly larvae (BSFL (L.)) are recognized for efficient biowaste reduction while yielding valuable proteins and fats for animals. However, lignocellulosic fibers in biowastes are difficult to digest by biowaste and larval digestive tract microorganisms as well as the larvae themselves. This study investigated two biowaste physical pretreatments (thermal, mechanical) for improving BSFL processing of fibrous biowastes. Cow manure, spent grain, and grass clippings were thermally pretreated at 90 °C for three durations (0.5, 1 and 4 h). Contrary to expectations, thermal pretreatment resulted in either no improvement or decreased larval performance on all substrates, regardless of treatment duration. In contrast, mechanical pretreatment of spent grain and grass clippings, involving milling with three screen sizes (0.5, 1 and 2 mm) showed promising results. Specifically, bioconversion rates on 0.5 mm-milled spent grain and grass clippings increased by 0–53 % and 25–44 % dry mass, respectively compared to untreated. Additionally, larval protein conversion increased by 41 % and 23 % on spent grain and grass clippings, respectively. However, mechanical pretreatment did not affect fiber degradation by larval conversion, as hemicellulose decreased by 25 % and 75 % for spent grain and grass clippings, respectively, regardless of particle size. Particle size reduction influenced substrate microbial respiration (CO mg/min), with 0.5-mm milled grass clippings exhibiting higher respiration compared to untreated, although this effect was not observed for spent grain. This study highlights mechanical pretreatment’s potential in enhancing BSFL bioconversion of fibrous biowastes and the importance of understanding substrate physical properties influencing substrate microorganisms and BSFL.

中文翻译：

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三种生物垃圾的物理预处理提高黑水虻幼虫生物转化效率

黑水虻幼虫 (BSFL (L.)) 被认为可以有效减少生物废物，同时为动物产生有价值的蛋白质和脂肪。然而，生物废物中的木质纤维素纤维很难被生物废物和幼虫消化道微生物以及幼虫本身消化。本研究调查了两种生物废物物理预处理（热、机械），以改善纤维生物废物的 BSFL 处理。将牛粪、酒糟和草屑在 90°C 下热处理三个持续时间（0.5、1 和 4 小时）。与预期相反，无论处理持续时间长短，热预处理在所有基质上都导致幼虫性能没有改善或下降。相比之下，对酒糟和草屑的机械预处理，包括使用三种筛网尺寸（0.5、1 和 2 毫米）进行研磨，显示出有希望的结果。具体而言，与未经处理的相比，0.5 毫米磨碎的酒糟和草屑的生物转化率干物质分别增加了 0-53% 和 25-44%。此外，幼虫在废弃谷物和草屑上的蛋白质转化率分别增加了 41% 和 23%。然而，机械预处理并不影响幼虫转化引起的纤维降解，因为无论颗粒大小如何，废谷物和草屑的半纤维素分别减少了 25% 和 75%。粒径减小影响基质微生物呼吸（CO 毫克/分钟），0.5 毫米磨碎的草屑与未经处理的草屑相比表现出更高的呼吸作用，尽管对于酒糟没有观察到这种影响。这项研究强调了机械预处理在增强纤维生物废物的 BSFL 生物转化方面的潜力，以及了解影响底物微生物和 BSFL 的底物物理特性的重要性。