Hydrothermal treatment for inactivating some hygienic microbial indicators from food waste–amended animal feed

To achieve the hygienic safety of food waste used as animal feed, a hydrothermal treatment process of 60–110 °C for 10–60 min was applied on the separated food waste from a university canteen. Based on the microbial analysis of raw waste, the inactivation of hygienic indicators of Staphylococcus aureus (SA), total coliform (TC), total aerobic plate counts (TPC), and molds and yeast (MY) were analyzed during the hydrothermal process. Results showed that indicators' concentrations were substantially reduced after hydrothermal treatment, with a greater reduction observed when the waste was treated with a higher temperature and pressure and a longer ramping time. The 110 °C hydrothermal treatment for 60 min was sufficient to disinfect food waste as animal feed from the viewpoint of hygienic safety. Results obtained so far indicate that hydrothermal treatment can significantly decrease microbial indicators' concentrations but does not lead to complete sterilization, because MY survived even after 60 min treatment at 110 °C. The information from the present study will contribute to the microbial risk control of food waste–amended animal feed, to cope with legislation on food or feed safety.

Implications: Reduction of microbial indicators at ramping time and holding time during the hydrothermal process showed that hydrothermal treatment is an effective method to achieve hygienic feed from food waste to a certain extent, but the conditions researched in this study were not enough for the complete sterilization of food waste, because of the different heat resistance of bacteria and spores.     

Dynamics of antibiotic resistance genes and microbial community in shortcut nitrification–denitrification process under antibiotic stresses

In this study, the performance of shortcut nitrification–denitrification (SCND) at different TC and SD stress conditions (0 μg/L, 1–97 days; 100 μg/L, 98–138 days; 500 μg/L, 139–175 days) was investigated. Higher level antibiotic stress (500 μg/L) led to the serious deterioration of nitrogen removal, and denitrification was more sensitive to antibiotic stress than nitrification. The dynamics of antibiotic resistance genes (ARGs) and microbial community were revealed by quantitative real-time PCR and 16S rDNA high-throughput sequencing, respectively. Tet-genes (tetA, tetQ, tetW), sul-genes (sulI, sulII), and mobile genetic element (intI1) in activated sludge increased by 1.2?~?2.5 logs with long-term exposure of antibiotic stress, and sulI, tetA, tetQ, and tetW were significantly positively correlated with intI1. Long-term antibiotics stress caused the decrease of most denitrifiers, and five genera were identified as the potential host of ARGs. The key impact factors of SCND drove the dynamics of ARGs and microbial community. Except for sulII gene, DO and FA were significantly positively correlated with ARGs, while FNA, NAR, and NO₂^?-N showed opposite effects to ARGs. Overall, maintaining relative lower DO, higher FNA, NAR, and NO₂^?-N conditions are not only benefit to the stable operation of SCND, but may also conducive to the control of ARG dissemination. This study provides theoretical basis on the control of ARGs in the SCND process.

     

Performance of CSTR–EGSB–SBR system for treating sulfate-rich cellulosic ethanol wastewater and microbial community analysis

Performance and microbial community composition were evaluated in a two-phase anaerobic and aerobic system treating sulfate-rich cellulosic ethanol wastewater (CEW). The system was operated at five different chemical oxygen demand (COD)/SO₄ ²⁻ ratios (63.8, 26.3, 17.8, 13.7, and 10.7). Stable performance was obtained for total COD removal efficiency (94.5%), sulfate removal (89.3%), and methane production rate (11.5 L/day) at an organic loading rate of 32.4 kg COD/(m³·day). The acidogenic reactor made a positive contribution to net VFAs production (2318.1 mg/L) and sulfate removal (60.9%). Acidogenic bacteria (Megasphaera, Parabacteroides, unclassified Ruminococcaceae spp., and Prevotella) and sulfate-reducing bacteria (Butyrivibrio, Megasphaera) were rich in the acidogenic reactor. In the methanogenic reactor, high diversity of microorganisms corresponded with a COD removal contribution of 83.2%. Moreover, methanogens (Methanosaeta) were predominant, suggesting that these organisms played an important role in the acetotrophic methanogenesis pathway. The dominant aerobic bacteria (Truepera) appeared to have been responsible for the COD removal of the SBR. These results indicate that dividing the sulfate reduction process could effectively minimize sulfide toxicity, which is important for the successful operation of system treating sulfate-rich CEW.

     

Characterisation of microbial activity in the framework of natural attenuation without groundwater monitoring wells?: a new Direct-Push probe

At many contaminated field sites in Europe, monitored natural attenuation is a feasible site remediation option. Natural attenuation includes several processes but only the microbial degradation leads to real contaminant removal and very few methods are accepted by the authorities providing real evidence of microbial contaminant degradation activity. One of those methods is the recently developed in situ microcosm approach (BACTRAP®). These in situ microcosms consist of perforated stainless steel cages or PTFE tubes filled with an activated carbon matrix that is amended with ¹³C-labelled contaminants; the microcosms are then exposed within groundwater monitoring wells. Based on this approach, natural attenuation was accepted by authorities as a site remediation option for the BTEX-polluted site Zeitz in Germany. Currently, the in situ microcosms are restricted to the use inside groundwater monitoring wells at the level of the aquifer. The (classical) system therefore is only applicable on field sites with a network of monitoring wells, and only microbial activity inside the monitoring wells at the level of the aquifer can be assessed. In order to overcome these limitations, a new Direct-Push BACTRAP probe was developed on the basis of the Geoprobe® equipment. With respect to the mechanical boundary conditions of the DP technique, these new probes were constructed in a rugged and segmented manner and are adaptable to various sampling concepts. With this new probe, the approach can be extended to field sites without existing monitoring wells, and microbial activity was demonstrated to be measureable even under very dry conditions inside the vadose zone above the aquifer. In a field test, classical and Direct-Push BACTRAPs were applied in the BTEX-contaminated aquifer at the ModelPROBE reference site Zeitz (Germany). Both types of BACTRAPs were incubated in the centre and at the fringe of the BTEX plume. Analysis of phospholipid fatty acid (PLFA) patterns showed that the bacterial communities on DP-BACTRAPs were more similar to the soil than those found on classical BACTRAPs. During microbial degradation of the ¹³C-labelled substrate on the carrier material of the microcosms, the label was only slightly incorporated into bacterial biomass, as determined by PLFA analysis. This provides clear indication for decreased in situ natural attenuation potential in comparison to earlier sampling campaigns, which is presumably caused by a large-scale source remediation measure in the meantime. In conclusion, Direct-Push-based BACTRAPs offer a promising way to monitor natural attenuation or remediation success at field sites which are currently inaccessible by the technique due to the lack of monitoring wells or due to a main contamination present within the vadose zone.     

Enhancing phytoextraction of Cd by combining poplar (clone “I-214”) with Pseudomonas fluorescens and microbial consortia

The plant–microorganism combinations may contribute to the success of phytoextraction of heavy metal-polluted soil. The purpose of this study was to investigate the effects of cadmium (Cd) soil concentration on selected physiological parameters of the poplar clone “I-214” inoculated at root level with a strain (BT4) of Pseudomonas fluorescens and a commercial product based on microbial consortia (Micosat F Fito®). Plants were subjected to Cd treatment of 40 mg kg^?1 in greenhouse. The effects of plant–microbe interactions, plant growth, leaf physiology, and microbial activity were periodically monitored. Metal concentration and translocation factors in plant tissues proved enhanced Cd uptake in roots of plants inoculated with P. fluorescens and transfer to shoots in plants inoculated with Micosat F Fito®, suggesting a promising strategy for using microbes in support of Cd uptake. Plant–microbe integration increased total removal of Cd, without interfering with plant growth, while improving the photosynthetic capacity. Two major mechanisms of metal phytoextraction inducted by microbial inoculation may be suggested: improved Cd accumulation in roots inoculated with P. fluorescens, implying phytostabilization prospective and high Cd transfer to shoots of inoculated plants, outlining enhanced metal translocation.     

Effects of conditioning,cross‐conditioning,and microbial growth on development of enhanced biodegradation of insecticides in soil

Abstract

Pretreatment of a Drummer‐Catlin soil mixture with granular formulations of carbofuran or trimethacarb enhanced biodegradation of subsequent treatments with the technical formulations. Degradation of carbofuran was enhanced by pretreatments with trimethacarb, and degradation of trimethacarb was enhanced by pretreatments with carbofuran. Bendiocarb degradation was enhanced by pretreatments of soil with carbofuran or trimethacarb. In bioassays with southern corn rootworm larvae, biological activity of carbofuran, trimethacarb, and bendiocarb was rapidly lost in soils pretreated with granular formulations. Pretreatment of soil with granular terbufos did not enhance the biodegradation of subsequent applications of technical terbufos. Several microbial biomass assays showed an increase in specific carbofuran‐degrading bacteria in soils that were pretreated with carbofuran. Bacteria were isolated that could grow on carbofuran and apparently degrade it when present with another carbon source.     

Does anthracene affect microbial activities and organic matter decomposition? A comparative study in Pinus halepensis litters from Mediterranean coastal and inland areas

The widespread concern about pollution caused by Polycyclic Aromatic Hydrocarbons (PAHs) raises the question of how they affect soil microbial communities which are potentially involved in the transformation of these pollutants. Using microcosms, we describe the effect of anthracene, a model PAH, on microbial communities inhabiting a Pinus halepensis litter from both coastal (COS) and inland (INL) Mediterranean sites. The microcosms were incubated over 3 months (25 °C, 60% WHC) and the effects of anthracene on microbial activities of both litters were monitored. Different enzyme activities (laccase, cellulase, β-glucosidase and acid phosphatase) and microbial respiration were measured and variations in litter chemical composition over incubation were determined using ¹³C Nuclear Magnetic Resonance (NMR) from both sites. Our results show that lignocellulolytic enzymes increased markedly after a 3-month incubation in COS microcosms, especially in the presence of anthracene, whereas INL microcosms were not similarly affected. These results show that anthracene not only has no toxic effect on the microbial activities tested but actually enhances the lignocellulolytic activities of the fungal communities from coastal litters, demonstrating the detoxification potential and resistance of stressed Mediterranean coastal ecosystems.     

Remediation of polycyclic aromatic hydrocarbon and metal-contaminated soil by successive methyl-β-cyclodextrin-enhanced soil washing–microbial augmentation: a laboratory evaluation

Polycyclic aromatic hydrocarbon (PAH) and metal-polluted sites caused by abandoned coking plants are receiving wide attention. To address the associated environmental concerns, innovative remediation technologies are urgently needed. This study was initiated to investigate the feasibility of a cleanup strategy that employed an initial phase, using methyl-β-cyclodextrin (MCD) solution to enhance ex situ soil washing for extracting PAHs and metals simultaneously, followed by the addition of PAH-degrading bacteria (Paracoccus sp. strain HPD-2) and supplemental nutrients to treat the residual soil-bound PAHs. Elevated temperature (50 °C) in combination with ultrasonication (35 kHz, 30 min) at 100 g MCD L^?1 was effective in extracting PAHs and metals to assist soil washing; 93 % of total PAHs, 72 % of Cd, 78 % of Ni, 93 % of Zn, 84 % of Cr, and 68 % of Pb were removed from soil after three successive washing cycles. Treating the residual soil-bound PAHs for 20 weeks led to maximum biodegradation rates of 34, 45, 36, and 32 % of the remaining total PAHs, 3-ring PAHs, 4-ring PAHs, and 5(+6)-ring PAHs after washing procedure, respectively. Based on BIOLOG Ecoplate assay, the combined treatment at least partially restored microbiological functions in the contaminated soil. The ex situ cleanup strategy through MCD-enhanced soil washing followed by microbial augmentation can be effective in remediating PAH and metal-contaminated soil.