Substrate Feeding Research Articles

Edible insects: Understanding benzo(a)pyrene toxicokinetics in yellow mealworms for safe and sustainable consumption

The global interest in edible insects as sustainable protein sources raises concerns about the bioaccumulation of contaminants, including polycyclic aromatic hydrocarbons (PAHs), to problematic levels. Understanding the accumulation dynamics of PAHs in edible insects is highly relevant due to the widespread sources and toxicological profiles; however, the bioaccumulative potential of PAHs in edible insects is unexplored. This study examined the uptake and elimination dynamics of benzo(a)pyrene (B(a)P), a representative and carcinogenic PAH, in yellow mealworm larvae (YMW, Tenebrio molitor). Larvae were exposed to feeding substrate with varying B(a)P concentrations (0.03, 0.3, and 3 mg kg−1), and uptake (21 days in B(a)P-contaminated substrate) and elimination (21 days in B(a)P-free substrate) kinetics were subsequently assessed. The results showed that YMW can eliminate B(a)P, revealing dose-dependent B(a)P bioaccumulation in these insects. Larvae fed on a substrate with 0.03 mg kg−1 accumulated B(a)P over 21 days, presenting values of 0.049 (Standard deviation - 0.011) mg kg−1 and a kinetic-based (BAFkinetic) of 1.93 g substrate g organism−1, exceeding the EU regulatory limits for food. However, with a B(a)P half-life (DT50) of 4.19 days in the larvae, an EU legislation safety criterion was met after a 13-day depuration period in clean substrate. Larvae exposed to substrates with 0.3 and 3 mg kg−1 showed B(a)P accumulation, with BAFkinetic values of 3.27 and 2.09 g substrate g organism−1, respectively, not meeting the current legal standards for food consumption at the end of the exposure to B(a)P. Although the B(a)P half-life values after 35 days were 4.30 and 10.22 days (DT50s), the larvae retained B(a)P levels exceeding permitted food safety limits. These findings highlight a significant oversight in regulating PAHs in animal feed and the need for comprehensive safety evaluations of PAH hazards in edible insects for improved PAH feeding guidelines.

Biogas Generation from Cotton Waste

Abstract: The anaerobic treatability and methane generation potential of three altered cotton wastes namely, cotton stalks, cotton seed hull and cotton oil cake remained determined in batch reactors. In addition, the effects of nutrient and trace metal supplementation were similarly investigated. The conversion of organics of cotton stem into bioenergy could serve the dual part of renewable energy production and waste reduction. Composition analysis demonstrated that cotton stem is a suitable feedstock for both bioethanol and biogas production. Anaerobic digestion of cotton stem attained 40.35% total biogas with 12.76% increased net CH4 volume compared to co-digestion of cotton stem with buffalo dung. Chopped cotton waste was considered as prospected substrate for biogas production. Cotton stalk was used gradually to exchange gobar content as substrate. During the study of four months the digester performed well till 90% feeding of cotton waste substrate. The maximum biogas generation detected was 1.3 m3 ; this shows that chopped cotton wastehas the potential to generate biogas. However, the digester was choked repeatedly and the concern of repetitive chocking of digester needs to be addressed.

An event triggered control scheme for enhanced production of Escherichia coli and biomass concentration during fed-batch cultivation

Control of a bioprocess is a challenging task mainly due to the nonlinearity of the process, the complex nature of microorganisms, and variations in critical parameters such as temperature, pH, and agitator speed. Generally, the optimum values chosen for critical parameters during Escherichia coli (E.coli) K-12fed-batch fermentation are37 ᵒC for temperature, 7 for pH, and 35 % for Dissolved Oxygen (DO). The objective of this research is to enhance biomass concentration while minimizing energy consumption. To achieve this, an Event-Triggered Control (ETC) scheme based on feedback-feed forward control is proposed. The ETC system dynamically adjusts the substrate feed rate in response to variations in critical parameters. We compare the performance of classical Proportional Integral (PI) controllers and advanced Model Predictive Control (MPC) controllers in terms of bioprocess yield. Initially, the data are collected from a laboratory-scaled 3L bioreactor setup under fed-batch operating conditions, and data-driven models are developed using system identification techniques. Then, classical Proportional Integral (PI) and advanced Model Predictive Control (MPC) based feedback controllers are developed for controlling the yield of bioprocess by manipulating substrate flow rate, and their performances are compared. PI and MPC-based Event Triggered Feed Forward Controllers are designed to increase the yield and to suppress the effect of known disturbances due to critical parameters. Whenever there is a variation in the value of a critical parameter, it is considered an event, and ETC initiates a control action by manipulating the substrate feed rate. PI and MPC-based ETC controllers are developed in simulation, and their closed-loop performances are compared. It is observed that the Integral Square Error (ISE) is notably minimized to 4.668 for MPC with disturbance and 4.742 for MPC with Feed Forward Control. Similarly, the Integral Absolute Error (IAE) reduces to 2.453 for MPC with disturbance and 0.8124 for MPC with Feed Forward Control. The simulation results reveal that the MPC-based ETC control scheme enhances the biomass yield by 7 %, and this result is verified experimentally. This system dynamically adjusts the substrate feed rate in response to variations in critical parameters, which is a novel approach in the field of bioprocess control. Also, the proposed control schemes help reduce the frequency of communication between controller and actuator, which reduces power consumption.

Nutritive value of feed substrate waste from black soldier fly larvae production, and its potential as an aquafeed ingredient

Abstract Black soldier fly larvae (BSFL, Hermetia illucens) are an alternative source of protein whereas little research has yet been conducted to investigate the potential application of feed substrate waste (FSW) from larval production in aquaculture. The nutritive value and physicochemical properties of FSW from BSFL were here investigated in vitro. Ten-day-old first-instar larvae were cultivated on two feed substrates: laying hen feed (FS I) or a laying hen feed-rice bran blend (1:1 w/w, FS II). FSW samples were collected at day 4.5 (0.5FSW) and day 9 (1FSW) of larval rearing, and compared to the original feed substrate (0FSW). Crude protein increased depending on FS type, harvesting time (HT), and their interaction. Crude lipid, crude fiber, acid detergent fiber, neutral detergent fiber, crude ash, nitrogen-free extract, and gross energy decreased (). Analysis of the physicochemical properties of FSW by various techniques (scanning electron microscopy, differential scanning colorimetry, X-ray diffractometry, and Fourier transform infrared spectroscopy) revealed qualitative and quantitative changes in FSW, driven by biological processes of BSFL. The digestibility of protein in FSW was determined by an in vitro protein digestibility (IVPD) test using crude digestive enzyme extracts from Nile tilapia (Oreochromis niloticus) and striped catfish (Pangasianodon hypophthalmus). 1FSW from FS I showed significantly better availability of protein relative to 0.5FSW (), while the IVPD of FSW from FS II was stable () or reduced (). Findings from this study suggest FSW from BSFL cultivation could be a protein source in aquafeed.

Performance of Hermetia illucens (Diptera: Stratiomyidae) larvae reared on organic waste diets and pupal chitin and chitosan yield.

Recently, much research has been oriented towards the influence of different food wastes and agricultural by-products on the final larval biomass and chemical composition of the insect species Hermetia illucens L.(Diptera: Stratiomyidae). However, there is a gap in the literature regarding the possible relationship between the feeding substrate of H. illucens larvae and chitin. In this context, in the present study, larvae of H. illucens derived from two populations (i.e.,UNIPI and UTH), were reared on different diets composed of fruits, vegetables, and meat. Based on the results, the larval survival was high for all diets tested. Larval growth in terms of weight gain, larval length, and feed conversion ratio (FCR) depended on the composition of each diet. The chitin and chitosan composition of larvae, reared on different substrates, did not reveal significant differences. Given the fact that the feeding substrate represent a significant cost in the industrial production of insects, its correlation with a high value product (i.e. chitosan) is important. On the other hand, as the prepupal stage of H. illucens is currently used as animal feed, the metabolization of chitin by farmed animals when the larvae or prepupae were offered as feed could have adverse effects. Thus, depending on the final product that is to be produced, industries could benefit from the establishment of a suitable diet.

Soft sensors based on interpretable learners for industrial-scale fed-batch fermentation: Learning from simulations

Monitoring bioprocesses is a challenging task where most of the variables of interest can only be measured offline. Soft sensors have emerged as a solution to provide online estimations. This work compares interpretable learners such as CART, M5, CUBIST, and Random Forest as soft sensors for industrial-scale fed-batch fermentation of penicillin production. A structured model of industrial-scale penicillin fermentation is implemented to generate the dataset and train the interpretable learners. Variables such as substrate feed rate, agitation, temperature, pH, dissolved oxygen, vessel volume, CO2, and O2 percent in off-gas are considered as independent (predictors). The CUBIST model has achieved the best results with values of 0.908, 9.916, 3.149, and 1.920 for the coefficient of determination, Mean Squared Error, Root Mean Squared Error, and Mean Absolute Error, respectively. These results demonstrate the feasibility of developing soft sensors based on interpretable models to predict penicillin concentration at an industrial scale.

Designing a High Gain Rectangular Microstrip Patch Antenna Working at 3 GHz for RADAR

This study presents the design and analysis of a microstrip patch antenna optimized for radar applications operating at a frequency of 3 GHz. The antenna is designed to meet the requirements of radar systems, offering characteristics such as high gain, low profile, and broad bandwidth. The design process involves simulation using electromagnetic simulation software to achieve the desired antenna performance parameters. Various antenna parameters, including substrate material selection, patch dimensions, feeding techniques, and impedance matching networks, are carefully optimized to enhance antenna performance. The proposed antenna design is expected to exhibit excellent radiation characteristics, making it suitable for radar applications requiring reliable and efficient communication at 3 GHz frequency. This antenna designed for operating at 3 GHz, type Rogers Ultralam1217 (tm) with dielectric constant, ∈r= 2.2 tanδ (0.0009) and thickness of h = 1.6mm. The antennas are simulated using Ansys HFSS software. The performance is evaluated in terms of return loss, gain, and directivity and is deemed to be compatible with simulations.

Elucidation of Palmarumycin Spirobisnaphthalene Biosynthesis Reveals a Set of Previously Unrecognized Oxidases and Reductases

AbstractSpirobisnaphthalenes (SBNs) are a class of highly oxygenated, fungal bisnaphthalenes containing a unique spiroketal bridge, that displayed diverse bioactivities. Among the reported SBNs, palmarumycins are the major type, which are precursors for the other type of SBNs structurally. However, the biosynthesis of SBNs is unclear. In this study, we elucidated the biosynthesis of palmarumycins, using gene disruption, heterologous expression, and substrate feeding experiments. The biosynthetic gene cluster for palmarumycins was identified to be distant from the polyketide synthase gene cluster, and included two cytochrome P450s (PalA and PalB), and one short chain dehydrogenase/reductase (PalC) encoding genes as key structural genes. PalA is an unusual, multifunctional P450 that catalyzes the oxidative dimerization of 1,8‐dihydroxynaphthalene to generate the spiroketal linkage and 2,3‐epoxy group. Chemical synthesis of key intermediate and in vitro biochemical assays proved that the oxidative dimerization proceeded via a binaphthyl ether. PalB installs the C‐5 hydroxy group, widely found in SBNs. PalC catalyzes 1‐keto reduction, the reverse 1‐dehydrogenation, and 2,3‐epoxide reduction. Moreover, an FAD‐dependent oxidoreductase, encoded by palD, which locates outside the cluster, functions as a 1‐dehydrogenase. These results provided the first genetic and biochemical evidence for the biosynthesis of palmarumycin SBNs.

Elucidation of Palmarumycin Spirobisnaphthalene Biosynthesis Reveals a Set of Previously Unrecognized Oxidases and Reductases.

Spirobisnaphthalenes (SBNs) are a class of highly oxygenated, fungal bisnaphthalenes containing a unique spiroketal bridge, that displayed diverse bioactivities. Among the reported SBNs, palmarumycins are the major type, which are precursors for the other type of SBNs structurally. However, the biosynthesis of SBNs is unclear. In this study, we elucidated the biosynthesis of palmarumycins, using gene disruption, heterologous expression, and substrate feeding experiments. The biosynthetic gene cluster for palmarumycins was identified to be distant from the polyketide synthase gene cluster, and included two cytochrome P450s (PalA and PalB), and one short chain dehydrogenase/reductase (PalC) encoding genes as key structural genes. PalA is an unusual, multifunctional P450 that catalyzes the oxidative dimerization of 1,8-dihydroxynaphthalene to generate the spiroketal linkage and 2,3-epoxy group. Chemical synthesis of key intermediate and in vitro biochemical assays proved that the oxidative dimerization proceeded via a binaphthyl ether. PalB installs the C-5 hydroxy group, widely found in SBNs. PalC catalyzes 1-keto reduction, the reverse 1-dehydrogenation, and 2,3-epoxide reduction. Moreover, an FAD-dependent oxidoreductase, encoded by palD, which locates outside the cluster, functions as a 1-dehydrogenase. These results provided the first genetic and biochemical evidence for the biosynthesis of palmarumycin SBNs.

Valorization of local agricultural by-products as nutritional substrates for Tenebrio molitor larvae: A sustainable approach to alternative protein production

In pursuit of sustainable protein sources, the agricultural sector and emerging edible insect industry intersect in the valorization of agricultural by-products. Establishing a mutually beneficial relationship involves utilizing agricultural by-products as feeding substrates for insect farming, potentially enhancing the sustainability of both sectors. In the present study, by-products from beer, rice, oat, maize, sunflower, and lucerne, as well as mill residues and spent mushroom substrate from the regions of Thessaly and Central Macedonia (Greece) were investigated as nutritional sources for the larvae of the yellow mealworm (Tenebrio molitor). Results show that the suitability of the tested by-products for rearing T. molitor larvae varies greatly, with larvae surviving better in some by-products than in others. The highest survival rate and the highest weight of larvae were recorded for larvae reared on rice bran, spent grains, and oat by-products. Similarly, high feed conversion and growth rate were observed when the larvae were fed with rice bran and spent grains. Thus, this research promotes cost-effective and sustainable T. molitor rearing, aligning with circular economy principles.

Metabolic performance and feed efficiency of black soldier fly larvae.

The black soldier fly (BSF), Hermetia illucens, is used in entomoremediation processes because its larvae can use a variety of organic residues with high efficiency. However, feed efficiencies are variable and characterized by uncertainties. Recently developed growth and metabolic performance models have predicted across different studies that BSF larvae have used 53%-58% of the feed components they have assimilated, in terms of carbon equivalents, for growth throughout their lifetime when reared on chicken feed. This is termed their average net growth efficiency. The remainder of the carbon has been lost as CO2. However, mass balances made under similar conditions show that the weight gained by BSF larvae corresponds to only 14%-48% of the feed substrates removed, indicating substrate conversion efficiency. Both performance indicators show even greater variability if more feed substrates are considered. Feed assimilation and growth rates, costs of growth, maintenance, and larval lifespan have been shown to affect how efficiently BSF larvae convert feed into growth. The differences between average net growth efficiencies and substrate conversion efficiencies further indicate that feed is often not used optimally in entomoremediation processes and that the overall yield of such processes is not determined by larval performance alone but is the result of processes and interactions between larvae, substrates, microbes, and their physical environment. The purpose of this study is to illustrate how quantification of the metabolic performance of BSF larvae can help improve our understanding of the role of the larvae in entomoremediation processes.

Optimization of Crystalline Xylose Production from Coffee Cherry Processing Waste

Purpose: This study aims to optimize the production of crystalline xylose from coffee cherry processing waste (CCPW) by investigating the influence of substrate concentration (SC), xylanase concentration (XC), and commercial xylose crystal concentration (CXC) on the process. Theoretical Reference: The research utilizes Response Surface Methodology (RSM) to design experiments and analyze the effects of SC, XC, and CXC on crystalline xylose production. Method: Experimental laboratory procedures were conducted with varying levels of SC (10-20%), XC (1-5%), and CXC (2-7%). Xylose production was carried out in fed-batch mode, with substrate feeding every 12 hours. Solvent volume was maintained at 250ml, with 60% added initially and the remaining 40% distributed incrementally during production. Results: The study found significant effects of XC and SC on xylose production, while CXC showed no significant influence. The optimized conditions were determined with SC at 10%, XC at 5%, and CXC at 7%, resulting in a xylose content of 0.804 g/L and a desirability value of 0.632. The model's validity was confirmed with a validation accuracy of 98.99%. Conclusion: The research demonstrates the effectiveness of RSM in optimizing crystalline xylose production from CCPW, highlighting the importance of XC and SC levels in the process. Implications of Research: The optimized conditions identified in this study offer practical insights for enhancing xylose production efficiency from CCPW, potentially contributing to the development of functional food ingredients and process engineering applications. Originality/Value: This study contributes to the field by providing a systematic approach to maximizing xylose production from coffee cherry processing waste, offering valuable knowledge for both academia and industry.

Valorization of black carrot pomace and pea powder for co-production of polygalacturonase and pectin lyase

AbstractPectic enzyme groups, particularly polygalacturonase and pectin lyase, are vital components of a high-value microbial enzyme category widely employed in applications within the fruit juice and wine industries. The exploration of alternative carbon and nitrogen sources remains crucial for enhancing enzyme production while reducing costs. This study evaluates the impact of carbon (black carrot pomace) and nitrogen (pea protein) loading on fermentable sugar content, protein content, and enzyme activities during both batch and fed-batch cultivation. Additionally, three distinct valorization techniques—thermal (steam), thermochemical (steam assisted with dilute acid), and microwave-assisted with dilute acid pretreatments—were assessed for their effectiveness in hydrolyzing black carrot pomace as a carbon source. The findings indicate that microwave-assisted dilute acid, coupled with enzymatic saccharification, resulted in the highest fermentable sugar production (0.493 g/g), achieving an 87.3% conversion yield. Pea protein demonstrated more favorable outcomes with the highest polygalacturonase activity (20.50 ± 0.52 U/L) and pectin lyase activity (46.44 ± 3.45 U/L) compared to whey protein and yeast extract used as nitrogen sources. Meanwhile, the highest polygalacturonase and pectin lyase activity, along with the highest total protein content (52.25 ± 0.06 mg/L), was recorded under the same culture conditions, reaching 164.34 ± 2.26 and 188.22 ± 1.72 U/L, respectively, after 72 h, representing approximately 1.18- and 1.34-fold increases from the batch system. Consequently, these results prove that fed-batch cultivation, utilizing black carrot pomace hydrolyzate as a feeding substrate and pea protein as a nitrogen source, significantly increases polygalacturonase and pectin lyase activity compared to batch cultivation.

Bioconversion of faecal and kitchen waste using black soldier fly larvae (Hermetia illucens):

Novel technologies to convert faecal waste into valuable nutrients provide a win-win situation in enhancing the closed sanitation loop, and providing safe sanitation. In this study, laboratory-scale experiments were set to examine the applicability of the Black Soldier Fly in bioconversion of organic matter (faecal matter (FM) and kitchen waste (KW) while producing larvae biomass rich in protein and fat compounds. To determine the mass balance process, each of the feed substrates (500g) in triplicate and 3 grams of 6-day-old larvae (844 larvae) were introduced. The larval developmental time to 50% pupation, survival rate (SR), waste reduction rates (WR), prepupal yield, bioconversion rate (BCR), feed conversion rate (FCR), and efficiency of digested feed (ECD) were monitored in triplicate at the end of the experiments for mass balance process. Mass balance determination (triplicate) yielded average prepupal yield of 70.43±0.02g and 56.77±0.01g, with protein content per unit ranging from 32.23% to 41.26% and 20.06% to 37.13% on faecal and kitchen waste respectively. The ECD of 17.63±0.01% and 12.05±0.00%, waste reduction of 79.91% and 92.24% from faecal and kitchen waste respectively were obtained. From the findings, both substrates were palatable as BSFL feeds. The study findings show the potential of using BSF larvae technology to valorise faecal and kitchen waste and produce larval biomass rich in proteins and fats.

Larval Frass of Hermetia illucens as Organic Fertilizer: Composition and Beneficial Effects on Different Crops.

Hermetia illucens has received a lot of attention as its larval stage can grow on organic substrates, even those that are decomposing. Black soldier fly breeding provides a variety of valuable products, including frass, a mixture of larval excrements, larval exuviae, and leftover feedstock, that can be used as a fertilizer in agriculture. Organic fertilizers, such as frass, bringing beneficial bacteria and organic materials into the soil, improves its health and fertility. This comprehensive review delves into a comparative analysis of frass derived from larvae fed on different substrates. The composition of micro- and macro-nutrients, pH levels, organic matter content, electrical conductivity, moisture levels, and the proportion of dry matter are under consideration. The effect of different feeding substrates on the presence of potentially beneficial bacteria for plant growth within the frass is also reported. A critical feature examined in this review is the post-application beneficial impacts of frass on crops, highlighting the agricultural benefits and drawbacks of introducing Hermetia illucens frass into cultivation operations. One notable feature of this review is the categorization of the crops studied into distinct groups, which is useful to simplify comparisons in future research.

Assessment of the Adsorption Activity of Bacterial Cells Using Yersinia pseudotuberculosis Model

Currently, the Russian Anti-Plague Institute “Microbe” produces diagnostic immunoglobulins used in laboratory diagnostics of plague pathogen. One of the important stages in obtaining this category of drugs is the process of adsorption and removal of cross-reacting antibodies to increase the specificity of the drug. For this purpose, inactivated cells of Yersinia pseudotuberculosis strains are used.The aim of the work was to assess the possibility of using immunochemical methods to analyze the adsorption properties of bacterial cells, followed by an assessment of the impact of cultivation method and conditions, and the variant of the strain used on the adsorption properties of bacterial cells.Materials and methods. Cultivation was carried out on solid and liquid nutrient media; cells were inactivated by temperature and chemical exposure. Adsorption activity was assessed using immunoblotting and inhibitory enzyme-linked immunosorbent assay. Statistical processing of the results was performed using two-factor analysis of variance.Results and discussion. The suitability of immunoblotting and inhibitory ELISA methods for qualitative and quantitative assessment of the adsorption properties of bacterial cells has been demonstrated. It has been established that the adsorption properties of bacterial cells are influenced by the method of inactivation and the application of substrate feeding; the method of cultivation does not affect the adsorption properties of cells.

Characterization of biochars of different origin and application to the anaerobic digestion of source-selected organic fraction of municipal solid waste under batch conditions and at different dosages

Anaerobic digestion (AD) is a wide-spread strategy to manage organic waste and recover valuable products but faces some limitations that could be overcome with additives like biochar (BC). The production of BC defines its properties, which in turn determine its effect on AD performance and methane yield. In this study, three biochars (BC1, BC2 and BC3) were characterized using several techniques (SEM imaging, BET, GC, ICP and FTIR). The properties of BC were found to be defined both by the feedstock and the production process. The BC were then applied to the AD of the organic fraction of municipal solid waste (OFMSW) using three doses (1, 5% and 10% w/w TS). Compared to the control, there was an increase in methane production in BC3 at doses 1% and 5% (+15 and +30%, respectively) and a decrease in BC1 and BC2 at 1% (−33% and −19%, respectively). The decrease in biogas production was often paired with an increased methane content. A two-way ANOVA analysis showed that the interaction of biochar dose and type had a significant effect on methane yield, meaning that the effect of BC on AD cannot be predicted with the dose or the type alone. When a second substrate feeding was performed, no significant differences on methane production were observed among the experimental conditions. Key aspects to properly assess the economic viability of the process have been also discussed. Further experiments could help to fill knowledge gaps and clarify the roles of BC characteristics and dose on AD performance.

Local agricultural by-products for rearing superworm larvae (Zophobas morio): a Greek example

Abstract As the industrial insect production sector is rapidly growing, the high production cost of insects forms a constraint for the further growth of the insect industry. One of the main factors that greatly contributes to the total insect production cost and affects the profitability of insect farms is feed costs. Various agricultural by-products have been successfully evaluated and proposed as low-cost, alternative, insect feedstocks. In this context, this study evaluates a variety of Greek agricultural by-products as feeding substrates for Zophobas morio (F.) (Coleoptera: Tenebrionidae) larvae. More specifically, eleven agricultural by-products derived from the seed cleaning process of barley, oats, peas and vetch and the production of cotton, sugar beet and sunflower, were utilized singly and as components of compound isonitrogenous diets at two nitrogen levels (2.7% and 3.2% on dry matter basis). The results showed that larvae reared on sunflower meal, oat and barley (class II) by-products performed well in terms of larval growth and survival. In contrast, for most other diets tested high mortality rates were recorded, indicating the necessity for the formulation of diets that meet the nutritional requirements of the larvae. Our study highlights the potential of locally available by-products for the rearing of Z. morio larvae and contributes to determining their nutrient requirements.

Potential Influence of Suspended Sediments on the Population Dynamics and Behavior of Filter-Feeding Brachycentrus occidentalis (Trichoptera: Brachycentridae) Larvae in a Southeastern Minnesota, USA, Trout Stream

Suspended and deposited sediments in streams can interfere with filter-feeding caddisfly larvae by reducing feeding sites and feeding efficiency, potentially lowering the densities, growth rates, and secondary production of an important trout prey. We conducted field studies at multiple stream sites with differing suspended-sediment loads, and a laboratory study was conducted under controlled conditions; together, these were designed to examine the role of suspended sediments in the population dynamics and behavior of Brachycentrus occidentalis (Trichoptera: Brachycentridae) larvae in a Minnesota, USA, trout stream. Stream sites that had elevated turbidities and elevated levels of suspended sediments also had significantly more fine bottom substrates and higher substrate embeddedness. In addition, Brachycentrus densities were reduced, growth rates were slower, secondary production was reduced, and the overall benthic macroinvertebrate taxa richness was lowest at the site with the highest suspended-sediment loading. Colder water temperatures at one site also influenced Brachycentrus production. In 24 h laboratory studies conducted in recirculating aquaria, the feeding activities of Brachycentrus larvae were reduced and their positioning altered under high turbidities (500 nephelometric turbidity units, NTU) relative to low turbidities (50 NTU or lower). High suspended-sediment loads have adversely affected filter-feeding caddisfly larvae by embedding and burying preferred coarse feeding substrates, altering their feeding positions and movements during the highest flows, and potentially impacting densities, growth rates, and secondary production.

Density-dependent development of the yellow mealworm Tenebrio molitor (Coleoptera: Tenebrionidae)

Abstract The increasing global population has led to high food demand and the interest for alternative resources is highly topical. The interest in utilizing insects as a source of food and feed has been rapidly increasing, as the on-growing population has made the need for protein even more demanding. Insect rearing is economically viable, since they can be fed with organic waste and agricultural by-products. The inclusion of bioactive compounds and active ingredients in insect diets has been identified as a potential key factor for enhancing their growth and performance. The aim of this study was to evaluate the effect of a diet enriched with functional ingredients of medicinal and aromatic plants and agricultural by-products of the Greek flora on the growth, survival and development of larvae of the yellow mealworm, Tenebrio molitor (Coleoptera: Tenebrionidae), in the context of larval density-induced stress. Wheat bran enriched with 5%, 10% or 20% of a prepared mixture containing post-distillation residues of medicinal and aromatic plants of the Greek flora (oregano, thyme, sage and rosemary, linseed oil, rock-samphire, industrial cannabis, and olive paste by-product) was evaluated as insect feeding substrate, whereas wheat bran alone (0% enrichment) served as control. Groups of 25, 50, 75 and 100 first instar larvae were separately collected, weighed, and put in cylindrical plastic cups to test if larval density had any effect on survival and development. According to our results, the final larval weight of T. molitor is significantly affected by the density of larvae but not by the rearing substrate. The highest individual weight among all tested substrates was achieved at the density of 25 larvae. Individual weights were highest when larvae were reared on 5% mixture. The weight of those reared on the control substrate was slightly lower, followed by the 10% and 20% mixtures. Larvae fed with 10% enriched substrate showed the highest survival rate, followed closely by those fed with the control and 5% substrates. Our results clearly demonstrate that larval survival is not density dependent, but density is important in the case of individual larval weight.