Influence of different inoculation densities of black soldier fly larvae (Hermetia illucens) on heavy metal immobilization in swine manure

Hormesis of black soldier fly larva: Influence and interactions in livestock manure recycling

Black soldier fly larvae (BSFL) are considered important organisms, utilized as tools to transform waste including manure into valuable products. The growth and cultivation of BSFL are influenced by various factors, such as the presence of toxic substances in the feed and parasites. These factors play a crucial role in hormesis, and contributing to regulate these contaminants hermetic doses to get sustainable byproducts. This review aims to understand the effects on BSFL growth and activities in the presence of compounds like organic and inorganic pollutants. It also assesses the impact of microbes on BSFL growth and explores the bioaccumulation of pharmaceutical compounds, specifically focusing on heavy metals, pesticides, pharmaceuticals, indigenous bacteria, insects, and nematodes. The review concludes by addressing knowledge gaps, proposing future biorefineries, and offering recommendations for further research.

Impacts of mixed ferrous sulfate-biochar additives on humification and bacterial community during electric field-assisted aerobic composting

This study assessed the impact of nine mixed ferrous sulfates and biochars on electric field-assisted aerobic composting (EAC), focusing on the spectroscopy of dissolved organic matter (DOM) and microbial communities. Adding 1.05% ferrous sulfate and 5.25% biochar to EAC increased the specific ultraviolet absorbances at 254 and 280 nm by 142.3% and 133.9% on day 35, respectively. This ratio accelerated the early response of carboxyl groups (-COOH) and lignin (CꘌC), enhancing the relative abundance of Thermobifida (4.0%) and Thermopolyspora (4.3%). The condition contributed to humus precursor formation on day 5, increasing the maximum fluorescence intensity of the humus-like component by 74.2% compared to the control on day 35. This study is the first to develop a combined and efficient organic and inorganic additive by multiple-variable experimentation for DOM humification. Consequently, it optimizes EAC for solid waste recycling.

Treatment of landfill leachate by black soldier fly (Hermetia illucens L.) larvae and the changes of intestinal microbial community

Black soldier fly larvae (BSFL) (Hermetia illucens) are commonly used to treat organic waste. This work aims to evaluate the transformation effect, heavy metal migration, and alterations in the gut microbiota of BSFL in addition to treating landfill leachate (LL) with BSFL. We found that BSFL may grow in various landfill leachate concentrations without obvious toxicity and growth inhibition. In addition, the results indicated a significant increase in the content of ammonia nitrogen and the activity of urease and β-glucosidase (β-GC) in LL, increased from 2570.17 mg/L to 5853.67 mg/L, 1859.17 mg/(g·d) to 517,177.98 mg/(g·d), 313.73 μg/(g·h) to 441.91 μg/(g·h) respectively. Conversely, the content of total nitrogen (TN) and total organic carbon (TOC) decreased in LL, decreasing by 31.24% and 29.45% respectively. Heavy metals are accumulated in the leachate by the BSFL to differing degrees, the descending sequence of accumulation is Cd > As > Cu > Cr. As dropped by 26.0%, Cd increased by 22.6%, Cu reduced by 5.23%, and Cr increased by 317.1% in the remaining matrix. The concentration of heavy metals satisfies the organic fertilizers' limit index (NY/T1978). The diversity of intestinal microorganisms in BSFL decreased, from 2819 OTUs to 2338 OTUs, with Providencia and Morganella emerging as the core flora. The gene abundance of nitrogen metabolism in the microbiota increased significantly. The TOC, β-GC, and Copper (Cu) content in BSFL correlated significantly with the gut microbiota. In Summary, this study revealed the treatment effect of BSFL on LL, the migration of heavy metals, and changes in the intestinal microorganisms of BSFL. The content of heavy metals in BSFL was found to be much lower than the upper limit of feed protein raw materials, demonstrating that BSFL is a sustainable method to treat LL.

Insects to the rescue? Insights into applications, mechanisms, and prospects of insect-driven remediation of organic contaminants

Traditional and emerging contaminants pose significant human and environmental health risks. Conventional physical, chemical, and bioremediation techniques have been extensively studied for contaminant remediation. However, entomo- or insect-driven remediation has received limited research and public attention. Entomo-remediation refers to the use of insects, their associated gut microbiota, and enzymes to remove or mitigate organic contaminants. This novel approach shows potential as an eco-friendly method for mitigating contaminated media. However, a comprehensive review of the status, applications, and challenges of entomo-remediation is lacking. This paper addresses this research gap by examining and discussing the evidence on entomo-remediation of various legacy and emerging organic contaminants. The results demonstrate the successful application of entomo-remediation to remove legacy organic contaminants such as persistent organic pollutants. Moreover, entomo-remediation shows promise in removing various groups of emerging contaminants, including microplastics, persistent and emerging organic micropollutants (e.g., antibiotics, pesticides), and nanomaterials. Entomo-remediation involves several insect-mediated processes, including bio-uptake, biotransfer, bioaccumulation, and biotransformation of contaminants. The mechanisms underlying the biotransformation of contaminants are complex and rely on the insect gut microbiota and associated enzymes. Notably, while insects facilitate the remediation of contaminants, they may also be exposed to the ecotoxicological effects of these substances, which is often overlooked in research. As an emerging field of research, entomo-remediation has several knowledge gaps. Therefore, this review proposes ten key research questions to guide future perspectives and advance the field. These questions address areas such as process optimization, assessment of ecotoxicological effects on insects, and evaluation of potential human exposure and health risks.

Dynamics of black soldier fly larvae composting - Impact of substrate properties and rearing conditions on process efficiency

Inadequate organic waste management have detrimental impact on the environment and on public health. Black soldier fly (BSF) larvae composting is a biological treatment for biodegradable waste that align with circular economy principles. The bioconversion efficiency of bio-waste into larval biomass is influenced by various factors, such as substrate type and the process parameters employed in the larval rearing process. In this study, the influence of these parameters on survival, material reduction (Mat.Red), waste-to-biomass conversion efficiency (BCE) and larval yield per rearing unit was investigated through two sets of experiments. In Experiment 1, the impact of larval density in five distinct rearing substrates was evaluated, while the effect of larval feed dose and substrate depth was assessed in Experiment 2, using a model substrate (dog food). In Experiment 1 it was found that higher larval density lead to an increase in BCE and larval yield, up to a threshold (around 6.25 larvae cm-2). Surpassing this threshold led to the production of smaller larvae, while the yield remained relatively consistent. In Experiment 2 it was found that supplying the substrate in a shallow layer (1-1.5 cm depth) and providing a low feed dose (0.1 g volatile solids (VS) larva-1) led to higher BCE and Mat.Red, albeit with a reduced overall yield per unit. Increasing feed load and substrate depth reduced the conversion efficiency, Mat.Red and larval survival. This study enhances the understanding of the effect of various process parameters used in the BSF larvae treatment, and how they interrelate.

The Variety of Applications of Hermetia illucens in Industrial and Agricultural Areas-Review

Hermetia illucens (Diptera: Stratiomyidae, Linnaeus, 1978), commonly known as the black soldier fly (BSF), is a saprophytic insect, which in recent years has attracted significant attention from both the scientific community and industry. The unrestrained appetite of the larvae, the ability to forage on various organic waste, and the rapid growth and low environmental impact of its breeding has made it one of the insect species bred on an industrial scale, in the hope of producing fodder or other ingredients for various animals. The variety of research related to this insect has shown that feed production is not the only benefit of its use. H. illucens has many features and properties that could be of interest from the point of view of many other industries. Biomass utilization, chitin and chitosan source, biogas, and biodiesel production, entomoremediation, the antimicrobial properties of its peptides, and the fertilizer potential of its wastes, are just some of its potential uses. This review brings together the work of four years of study into H. illucens. It summarizes the current state of knowledge and introduces the characteristics of this insect that may be helpful in managing its breeding, as well as its use in agro-industrial fields. Knowledge gaps and under-studied areas were also highlighted, which could help identify future research directions.

Toxic Effects of Industrial Flocculants Addition on Bioconversion of Black Soldier Fly Larvae (Hermetia illucens L.)

Simple Summary

The black soldier fly (BSF) is a saprophagous insect that has been applied to organic waste management while providing high-quality insect protein. Flocculants are widely present in organic wastes that could be treated by black soldier fly larvae (BSFL), such as food wastes, municipal sludge, and cyanobacteria sludge. This study investigated the effect of flocculants on bioconversion of BSFL. The results showed that the addition of flocculant affected the bioconversion efficiency and nutritional composition of BSFL. The relative abundance of bacterial genera related to lipid metabolism decreased with increasing flocculant concentrations while disease-related taxa increased in relative abundance. This study could serve as a reference for related research and applications in the future.

Abstract

Black soldier fly is a saprophagous insect that has been widely reported in recent years due to its excellent performance in bioremediation. Due to the widespread presence of flocculants in the organic waste treated by black soldier fly larvae, this study aimed to evaluate the potential impacts and risks of flocculant addition (a combination of poly aluminum chloride and polyacrylamide with the ratio of 50:1). Results showed that the growth and weight of BSFL in the high-exposure groups (≥200 mg/L) were inhibited. The bioaccumulation of aluminum (Al) in larvae was estimated, and the proportions of different Al forms in the frass from high to low were the residual state (41.38% to 67.92%), water-soluble state (16.88% to 37.03%), acid-soluble state (8.45% to 18.72%), and alkali-soluble state (3.38% to 5.14%). The relative abundance of bacterial genera related to lipid metabolism decreased with increasing flocculant concentrations while disease-related taxa increased in relative abundance. The results serve as a reference for subsequent research and application of the treatment of flocculant-contaminated waste by BSFL.