Degree of Hydrolysis Affects the Techno-Functional Properties of Lesser Mealworm Protein Hydrolysates

Protein hydrolysates from lesser mealworm (Alphitobius diaperinus, LM) were obtained by enzymatic hydrolysis with protease from Bacillus licheniformis. A preliminary test performed for five hours of hydrolysis generated an insect protein hydrolysate with 15% of degree of hydrolysis (DH), optimum solubility property and oil holding capacity, but emulsifying and foaming ability were completely impaired. In order to investigate the potential implication of DH on techno-functional properties, a set of protein hydrolysates with a different DH was obtained by sub-sampling at different time points during three hours of enzymatic hydrolysis process. An increase in DH% had positive effects on the solubility property and oil holding ability, while a reduced emulsifying ability was observed up to five hours of hydrolysis. These results demonstrated that the enzymatic hydrolysis, if performed under controlled conditions and not for a long period, represents a valid method to extract high quality protein from insects with tailored techno-functionality, in order to produce tailored ingredients for feed and food purpose

Monitoring the injection of microscale zerovalent iron particles for groundwater remediation by means of complex electrical conductivity imaging

The injection of microscale zerovalent iron (mZVI) particles for groundwater remediation has received much interest in recent years. However, to date, monitoring of mZVI particle injection is based on chemical analysis of groundwater and soil samples and thus might be limited in its spatiotemporal resolution. To overcome this deficiency, in this study, we investigate the application of complex electrical conductivity imaging, a geophysical method, to monitor the high-pressure injection of mZVI in a field-scale application. The resulting electrical images revealed an increase in the induced electrical polarization (∼20%), upon delivery of ZVI into the targeted area, due to the accumulation of metallic surfaces at which the polarization takes place. Furthermore, larger changes (>50%) occurred in shallow sediments, a few meters away from the injection, suggesting the migration of particles through preferential flowpaths. Correlation of the electrical response and geochemical data, in particular the analysis of recovered cores from drilling after the injection, confirmed the migration of particles (and stabilizing solution) to shallow areas through fractures formed during the injection. Hence, our results demonstrate the suitability of the complex conductivity imaging method to monitor the transport of mZVI during subsurface amendment in quasi real-time

Dynamics of an Oligotrophic Bacterial Aquifer Community during Contact with a Groundwater Plume Contaminated with Benzene, Toluene, Ethylbenzene, and Xylenes: an In Situ Mesocosm Study{dagger}

An in situ mesocosm system was designed to monitor the in situ dynamics of the microbial community in polluted aquifers. The mesocosm system consists of a permeable membrane pocket filled with aquifer material and placed within a polypropylene holder, which is inserted below groundwater level in a monitoring well. After a specific time period, the microcosm is recovered from the well and its bacterial community is analyzed. Using this system, we examined the effect of benzene, toluene, ethylbenzene, and xylene (BTEX) contamination on the response of an aquifer bacterial community by denaturing gradient gel electrophoresis analysis of PCR-amplified 16S rRNA genes and PCR detection of BTEX degradation genes. Mesocosms were filled with nonsterile or sterile aquifer material derived from an uncontaminated area and positioned in a well located in either the uncontaminated area or a nearby contaminated area. In the contaminated area, the bacterial community in the microcosms rapidly evolved into a stable community identical to that in the adjacent aquifer but different from that in the uncontaminated area. At the contaminated location, bacteria with tmoA- and xylM/xylE1-like BTEX catabolic genotypes colonized the aquifer, while at the uncontaminated location only tmoA-like genotypes were detected. The communities in the mesocosms and in the aquifer adjacent to the wells in the contaminated area consisted mainly of Proteobacteria. At the uncontaminated location, Actinobacteria and Proteobacteria were found. Our results indicate that communities with long-term stability in their structures follow the contamination plume and rapidly colonize downstream areas upon contaminatio

Impact of chemical oxidants on the heavy metals and the microbial population in sediments

In this study, chemical oxidation was applied to treat three contaminated sediments. All the sediments were contaminated with mineral oil, polycyclic aromatic hydrocarbons and heavy metals and had an organic matter content ranging from 2.4 to 7.6 %. The natural oxidant demand of the sediments was determined during treatment with two different types of oxidants (potassium permanganate and sodium persulfate), and the effect of these oxidants on the heavy metal release and on the microbial community was investigated. The natural oxidant demands of the sediments under persulfate treatment were lower (30-100 g kg(-1)) than the ones treated with permanganate (50-450 g kg(-1)). Cr was released during the application of permanganate whereas Zn and Pb were released under persulfate treatment. qPCR results showed that permanganate and persulfate, both at a concentration of 150 g kg(-1), caused a decrease (2 log units) in the number of 16S rRNA gene of total bacteria in the sediment having the lowest organic matter content. However, the total ATP, considered as a biomarker for microbial activity, was below detection limit in all sediments in the presence of at least 150 g kg(-1) oxidant. Only permanganate induced a shift in the structure of the microbial community

Microbial Community Characterization in a Pilot-Scale Permeable Reactive Iron Barrier

A 2-year-old pilot-scale zerovalent iron (Fe-0)-permeable reactive barrier, treating groundwater contaminated with tetrachloroethylene and trichloroethylene, was microbially characterized using DNA-based polymerase chain reaction-DGGE (denaturing gradient gel electrophoresis) analysis. In situ mesocosm systems positioned in monitoring wells at different locations in the pilot-scale system allowed core sampling as a function of time without disturbing the barrier performance. Mesocosms were harvested from each location after 3, 7, and 23 months of operation and revealed the presence of Eubacteria, Archaea, and different functional groups of bacteria, which might affect iron barrier performance, including sulfate-reducing bacteria, iron(III)-reducing bacteria, denitrifying bacteria, and methanogens. DGGE fingerprints of the eubacterial 16S rDNA polymerase chain reaction amplification products clearly indicated different community structures in the iron material compared with the aquifer material. Gene sequencing of two dominant bands observed in samples collected from the iron barrier showed a maximum sequence similarity of 97% and 94% with a Firmicutes bacterium and an iron(III)-reducing bacterium enrichment culture clone, respectively. Results indicate that Fe-0 had a profound impact on the microbial community composition, most likely by decreasing the redox potential and increasing the pH of the groundwater

Harvesting of microalgae: Overview of process options and their strengths and drawbacks

Microalgae harvesting is a major challenge because microalgal cells are small and carry a negative surface charge and biomass concentration in cultures is relatively low. The microalgal biomass (0.05%, w/w) needs to be concentrated to a paste with 15%–25% water content. This dewatering process is ideally performed in two stages, including a first preconcentration step in combination with a second dewatering step. Microalgae are a very heterogeneous group of organisms differing in size and shape and culture conditions. Applications of microalgal biomass range from low-value (biofuels) to high-value applications (nutraceuticals). It is therefore likely that the optimal harvesting technology differs between species, culture conditions, or the final application of the biomass. Harvesting should not cause contamination of the biomass or influence biomass quality. Finally, water recycling to reduce the water footprint is an important aspect to include into the harvesting process. This chapter gives an overview of several harvesting process options with the focus on their strengths and highlighting the aforementioned aspects.status: publishe