Jozef Coosemans

Microbiological aspects of biowaste during composting in a monitored compost bin

Aims: To determine the microbial succession of the dominating taxa and functional groups of microorganisms and the total microbial activity during the composting of biowaste in a monitored process.

Bioremediation of diesel oil-contaminated soil by composting with biowaste

Soil spiked with diesel oil was mixed with biowaste (vegetable, fruit and garden waste) at a 1:10 ratio (fresh weight) and composted in a monitored composting bin system for 12 weeks. Pure biowaste was composted in parallel. In order to discern the temperature effect from the additional biowaste effect on diesel degradation, one recipient with contaminated soil was hold at room temperature, while another was kept at the actual composting temperature. Measurements of composting parameters together with enumerations and identifications of microorganisms demonstrate that the addition of the contaminated soil had a minor impact on the composting process. The first-order rate constant of diesel degradation in the biowaste mixture was four times higher than in the soil at room temperature, and 1.2 times higher than in the soil at composting temperature.

Inactivation of Salmonella Senftenberg strain W 775 during composting of biowastes and garden wastes

Aims:  Determination of the minimum requirements (time–temperature relationship and moisture content) that are needed for a sufficient eradication of an indicator organism.

Synergistic antifungal activity of two chitin-binding proteins from spindle tree (Euonymus europaeus L.)

Two structurally different chitin-binding proteins were isolated from bark and leaves of the spindle tree (Euonymus europaeus L.). Both the small hevein-like chitin-binding protein (Ee-CBP) and the classical class-I chitinase (Ee-chitinase) possess antifungal properties, Ee-CBP being far more potent than Ee-chitinase. In addition, Ee-CBP and Ee-chitinase display a pronounced synergistic effect when added together in the test medium. Determination of the biological activities indicates that the synergism between Ee-CBP and Ee-chitinase relies on a different mode of action. Cloning and sequencing of the corresponding genes further revealed that Ee-CBP and Ee-chitinase are simultaneously expressed in bark and leaf tissues, and hence can act synergistically in planta. Moreover, analysis of the deduced sequences allowed the exact relationship between the structurally different Ee-CBP and Ee-chitinase to be corroborated. Both proteins are synthesized as similar chimeric precursors consisting of an N-terminal hevein domain linked to a C-terminal chitinase-like domain by a hinge region. However, whereas in the case of Ee-chitinase the C-terminal chitinase domain remains linked to the N-terminal hevein domain, the corresponding domain is cleaved from the Ee-CBP-precursor resulting in the formation of the hevein-type Ee-CBP. Since both precursors are—apart from the hinge region between the hevein and chitinase domains—very similar, the Ee-CBP/Ee-chitinase system offers a unique opportunity to study the importance of sequence and/or structural information comprised in the hinge region for the posttranslational processing of the respective precursor proteins.

The fate of plant pathogens and seeds during anaerobic digestion and aerobic composting of source separated household wastes

Anaerobic digestion is becoming a more common method for treatment of organic wastes. Little is known, however, about the effects of this process on the fate of plant pathogens and seeds. Therefore, the fates of the plant pathogens Plasmodiophora brassicae, Heterodera schachtii, Meloidogyne incognita, Ralstonia solanacearum, tobacco mosaic virus (TMV) and tomato seeds were followed during anaerobic digestion of source separated household wastes. With the exception of TMV, all test organisms were destroyed to below detectable limits within one day of anaerobic digestion at 52°C. Two days of anaerobic digestion did not reduce the concentration of TMV. However, two days of anaerobic digestion followed by 19 days of high temperature composting at 58°C reduced the concentration of infectious TMV particles by a factor of almost three orders. Anaerobic digestion followed by 12 days of composting at 68°C was even more effective. Although TMV concentrations were not eliminated entirely, we conclude that short-term high temperature anaerobic digestion followed by high temperature composting is a highly efficient process for the eradication of detrimental agents from solid wastes.

Systemic Resistance Induced in Cucumber Against Pythium Root Rot by Source Separated Household Waste And Yard Trimmings Composts

Disease control with compost often is attributed to four factors including competition, antibiosis, parasitism and induced systemic resistance (ISR). Induction of systemic resistance by source separated household waste and yard trimmings compost against Pythium root rot of cucumber caused by Pythium ultimum was studied in a split-root bioassay. Split-root pairings were tested in root rot potting soil paired with potting soil, compost-amended potting soil suppressive to root rot paired with the potting soil, and compost-amended potting soil paired with the compost-amended potting soil. Only one side of the split roots was infested with P. ultimum. Root rot, based on dry and fresh root weights, was significantly reduced in split roots of plants produced in the conducive infested potting soil paired with the suppressive yard trimmings compost-amended mix. This suggested that systemic effects were induced in the roots by the suppressive compost against Pythium root rot. Growth of transplants germinated in the source separated household waste compost mix was significantly better than those germinated in the potting soil. Finally, root rot of plants germinated in the suppressive mix and then transplanted into the conducive mix was also significantly less severe than that of plants germinated in the conducive mix.

Simple ion chromatographic method for the determination of chlormequat residues in pears

Current methods for quantitative determination of chlormequat residues in food crops are characterized by rather low recoveries and the need for derivatization (in case of gas chromatography, GC), or by high capital investment (in case of liquid chromatography-mass spectrometry, LC-MS). We propose a cation-exchange chromatography method for the analysis of chlormequat in pears. The method is based on extraction of the target compound with 40 mM HCl, followed by centrifugation and filtration. The filtrate is directly injected into an ion chromatograph equipped with a commercially available cation-exchange column and a suppressed conductivity detection system. While the limit of detection (LOD) (0.5 mg/kg) may not be small enough to allow dietary analysis, the method meets all validation requirements and is an alternative for the existing GC and LC-MS methods in quality control.

Cannabiorci- and 8-chlorocannabiorcichromenic acid as fungal antagonists from Cylindrocarpon olidum

Cannabiorcichromenic acid and 8-chlorocannabiorcichromenic acid [8-chloro-5-hydroxy-2,7-dimethyl-2-(4-methyl-3-pentenyl)-2H-1-benzopyran -6- carboxylic acid] were identified as active components in cultures of Cylindrocarpon olidum which antagonized various other fungi. Experiments performed with the purified acids confirmed the antifungal activity; in addition, they revealed that the acids had antibiotic properties towards gram-positive bacteria and were toxic to nematodes.

Compost Microbial Activity Related to Compost Stability

In this chapter, compost stability has been reviewed in general and in relation to microbial activity. The evolution of microbial activity during composting is discussed. Another issue that has been reviewed is the relationship between temperature and microbial activity during the composting of biowaste. Different methods to measure compost stability, as well as chemical, physical and biological methods have been considered. Moreover, an overview is given about the implications of the use of non-stabilized compost and about the benefits of the use of compost in agriculture.

The Fate of Plant Pathogens and Seeds During Backyard Composting of Vegetable, Fruit and Garden Wastes

Backyard composting is widely used to process vegetable, fruit and garden wastes (biowastes) in gardens. Unfortunately, little is known about the hygienisation efficiency during this small-scale composting process. In a 6-month experiment, the eradication of tobacco mosaic virus (TMV), Plasmodiophora brassicae, Heterodera schachtii and of tomato seeds was followed during corn-posting in four 200–1 vessels. In conformity with the German BioAbfV norms which were used as guideline for this research, the pathogens were incorporated as TMV-infected tobacco leaves, as a mixture of clubroot-infected cauliflower roots and infested soil, as cysts or as seeds packed in nylon fibre nets. Two vessels were totally filled; two others were half-filled. At the end of the 6-month composting period, only TMV was completely eliminated, while H. schachtii and the tomato seeds were almost completely eliminated. On the other hand, P. brassicae survived the composting process. Destruction of the tomato seeds, of TMV and of H. schachtii could partly be explained on the basis of heat treatment. Other factors may have contributed to the sanitising effect observed during this rather low-temperature composting process.