Quantification of viable but nonculturable <i>Salmonella</i>
 spp. and <i>Shigella</i>
 spp. during sludge anaerobic digestion and their reactivation during cake storage

Fu, Bo; Qian, Jiang; Liu, H.-B.; Liu, H.

doi:10.1111/jam.12887

Cited by 19 publications

(9 citation statements)

References 24 publications

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“…19,20 It is also well-established that anaerobic digester treatment can suppress human pathogen population The algae strain was only added to one set of bioreactors but all bioreactors under this heading were part of the same batch sizes, 21,22 however, recent literature suggests that many pathogens enter a viable but non-culturable state during digestion. 23 Thus, it would be important to implement a pathogen monitoring program for wastewater treated by anaerobic digestion followed by algae cultivation. This is particularly relevant if the water will be re-used in agricultural settings.…”

Section: Discussionmentioning

confidence: 99%

Algal–bacterial synergy in treatment of winery wastewater

et al. 2018

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There is significant potential for employing algae in tertiary wastewater treatment, however, little is known about the contribution of algae-bacteria synergy toward treatment performance. This study demonstrates potential synergy in the treatment of three winery wastewater samples. Two strains of green algae, Auxenochlorella protothecoides and Chlorella sorokiniana were tested and each removed > 90% of nitrogen, > 50% of phosphate, and 100% of acetic acid in the wastewater. Both algae strains grew significantly faster on wastewaters compared to growth on minimal media. Organic carbon in the wastewater apparently played a limited role in algal growth enhancement. When cultured on sterile-filtered wastewater, A. protothecoides increased soluble COD loadings in two of the three wastewaters and C. sorokiniana secreted an insoluble film. Culturing algae with the native wastewater microbial community negated the secretion of algal photosynthate, allowing for simultaneous reductions in COD and nutrient concentrations. Both algae species stimulated bacterial growth in a strain-specific way, suggesting unique responses to algal photosynthate. Cofactor auxotrophy for thiamine, cobalamin, and biotin is widespread among algae and these cofactors are typically obtained from bacteria. Sequencing the wastewater microbial community revealed bacteria capable of synthesizing all three cofactors while liquid chromatography with mass spectrometry (LCMS) and bio-assays revealed the presence of thiamine metabolites in the wastewaters. These cofactors likely increased algal growth rates, particularly for A. protothecoides, which cannot synthesize thiamine de-novo but can salvage it from degradation products. Collectively, these results demonstrate that bacteria and algae provided synergistic growth benefits, potentially contributing to higher levels of wastewater treatment than either organism type alone.

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Section: Discussionmentioning

confidence: 99%

Algal–bacterial synergy in treatment of winery wastewater

et al. 2018

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“…In environmental conditions, bacteria are submitted to various stresses and lose their culturability, what has been called a Viable but Non-culturable (VBNC) state ( Oliver, 2010 ; Li et al, 2014 ). To circumvent their loss of culturability, several authors have used DNA-based quantification (qPCR) to study bacteria in environmental samples such as soil, wastewater, sludge, manure or compost ( Wéry et al, 2008 ; Klein et al, 2011 ; Fu et al, 2015 ). One of the main criticisms of the use of qPCR for quantifying live bacteria in environmental samples is that it may overestimate the concentration of viable bacteria since extracellular DNA or DNA from non-viable cells can also produce a PCR signal ( Nocker and Camper, 2006 ).…”

Section: Discussionmentioning

confidence: 99%

“…In fact, several studies have demonstrated that pathogens can enter into a Viable but Non-Culturable (VBNC) state in biosolids or animal by-products after various treatments, including the AD process ( Higgins et al, 2007 ; Qi et al, 2008 ; Viau and Peccia, 2009 ; Fu et al, 2014 ; Desneux et al, 2016 ). Fu et al (2015) demonstrated the induction of a VBNC state of Salmonella sp. and Shigella sp.…”

Section: Introductionmentioning

confidence: 99%

“…The behavior of pathogens during AD has been studied by several authors ( Smith et al, 2005 ; Wagner et al, 2009 ; Avery et al, 2014 ; Fu et al, 2015 ). Temperature appears to be the main factor affecting pathogen viability during AD ( Wagner et al, 2009 ).…”

Section: Introductionmentioning

confidence: 99%

“…However, very little information about the viability of pathogens during the storage of digestates has been reported. Furthermore, some studies have shown potential regrowth of coliforms and pathogens during the storage of compost ( Sidhu et al, 2001 ; Pietronave et al, 2004 ), biowaste ( Gibbs et al, 1995 ; Bagge et al, 2005 ) or digestate ( Fu et al, 2015 ; Orzi et al, 2015 ). Sidhu et al (2001) did not observe a decline of Salmonella sp.…”

Section: Introductionmentioning

confidence: 99%

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Persistence and Potential Viable but Non-culturable State of Pathogenic Bacteria during Storage of Digestates from Agricultural Biogas Plants

et al. 2016

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Despite the development of on-farm anaerobic digestion as a process for making profitable use of animal by-products, factors leading to the inactivation of pathogenic bacteria during storage of digestates remain poorly described. Here, a microcosm approach was used to evaluate the persistence of three pathogenic bacteria (Salmonella enterica Derby, Campylobacter coli and Listeria monocytogenes) in digestates from farms, stored for later land spreading. Nine samples, including raw digestates, liquid fractions of digestate and composted digestates, were inoculated with each pathogen and maintained for 40 days at 24°C. Concentrations of pathogens were monitored using culture and qPCR methods. The persistence of L. monocytogenes, detected up to 20 days after inoculation, was higher than that of Salmonella Derby, detected for 7–20 days, and of C. coli (not detected after 7 days). In some digestates, the concentration of the pathogens by qPCR assay was several orders of magnitude higher than the concentration of culturable cells, suggesting a potential loss of culturability and induction of Viable but Non-Culturable (VBNC) state. The potential VBNC state which was generally not observed in the same digestate for the three pathogens, occurred more frequently for C. coli and L. monocytogenes than for Salmonella Derby. Composting a digestate reduced the persistence of seeded L. monocytogenes but promoted the maintenance of Salmonella Derby. The effect of NH4+/NH3 on the culturability of C. coli and Salmonella Derby was also shown. The loss of culturability may be the underlying mechanism for the regrowth of pathogens. We have also demonstrated the importance of using molecular tools to monitor pathogens in environmental samples since culture methods may underestimate cell concentration. Our results underline the importance of considering VBNC cells when evaluating the sanitary effect of an anaerobic digestion process and the persistence of pathogens during the storage of digestates and subsequent land spreading.

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