Press Xenobiotic 3-Chloroaniline Disturbance Favors Deterministic Assembly with a Shift in Function and Structure of Bacterial Communities in Sludge Bioreactors

Thi

et al. 2022

Preprint

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The use of food-processing wastewaters to produce microbial biomass-derived single cell protein (SCP) is a sustainable way to meet the global food demand. Yet, despite the potential benefits of lower costs and greater resource recovery compared to pure cultures, bioconversion processes relying on microbial community-based approaches to SCP production have received scarce attention. Here, we evaluated SCP production from soybean-processing wastewaters under controlled reactor conditions using the existent microbial communities in these wastewaters. Six sequencing batch reactors of 4.5-L working volume were operated at 30 ℃ for 34 d in cycles consisting of 3-h anaerobic and 9-h aerobic phases. Four reactors received no microbial inoculum and the remaining two were amended with a 1.5 L of mixed culture from a prior microbial community-based SCP production. Microbial characterization was done via 16S rRNA gene metabarcoding. Influent wastewater batches had variable chemical characteristics but a similar microbial composition. Reactors produced more SCP when fed with wastewaters of higher soluble total Kjeldahl nitrogen (sTKN) content and a lower carbon-to-nitrogen ratio (sCOD:sTKN). The biomass protein yield ranged from 0.24 to 3.13 g protein/g sTKN, with a maximum protein content of 50%. An average of 92% of sCOD and 73% of sTN removal was achieved. Distinct microbial communities were enriched in all six bioreactors after 34 d, where the prevailing genera included Azospirillum, Rhodobacter, Lactococcus, Novosphingobium, and Acidipropionibacterium. In contrast, the microbial community of influent wastewaters was dominated by Lactococcus and Weissella. We showed that constituents in soybean wastewater can be converted to SCP through microbial community-based growth processes and demonstrated the effect of variable influent wastewater composition on SCP production.

Section: Methodsmentioning

confidence: 99%

Microbial community-based production of single cell protein from soybean-processing wastewater of variable chemical composition

Vethathirri

Thi

et al. 2022

Preprint

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“…A microbial community-based approach to build SCP has several potential advantages over axenic culturing (Vethathirri et al, 2021), such as a higher protein content due to synergistic interactions between different SCP-producing microorganisms and the utilization of various carbon and nitrogen sources available in the substrate (Alloul et al, 2021a; Vethathirri et al, 2022), the accumulation of intracellular components (Li et al, 2022), and process stability in terms of resistance and resilience to disturbances (Santillan et al, 2020a; Santillan et al, 2020b; Santillan et al, 2021). The microbial composition of the microbial community-based SCP employed in the experimental diet was dominated by the genera Acidipropionibacterium and Propioniciclava (Figure 2), which have potential as probiotics and producers of valuable metabolites.…”

Section: Resultsmentioning

confidence: 99%

Microbial community-based bacterial protein from soybean-processing wastewater as a value-added alternative fish feed ingredient for Asian sea bass (Lates calcarifer)

Yasumaru

Vethathirri

et al. 2023

Preprint

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As the global demand for food increases, aquaculture plays a key role as the fastest growing animal protein sector. However, existing aquafeeds contain protein ingredients that are not sustainable under current production systems. We evaluated the use of microbial community-based single cell protein (SCP), produced from soybean processing wastewater, as a partial fishmeal protein substitute in juvenile Asian seabass (Lates calcarifer). A 24-day feeding trial was conducted with a control fishmeal diet and a 50% fishmeal replacement with microbial community-based SCP as an experimental group, in triplicate tanks containing 20 fish each. Both diets met the protein, essential amino acids (except for lysine), and fat requirements for juvenile Asian sea bass. The microbial composition of the SCP was dominated by the generaAcidipropionibacteriumandPropioniciclava, which have potential as probiotics and producers of valuable metabolites. The growth performance in terms of percent weight gain, feed conversion ratio (FCR), specific growth rate (SGR), and survival were not significantly different between groups after 24 days. The experimental group had less variability in terms of weight gain and FCR than the control group. Overall, microbial community-based protein produced from soybean processing wastewater has potential as a value-added feed ingredient for sustainable aquaculture feeds.

“…In our earlier work the presence of 3-chloroaniline had served as a disturbance 9 , since chlororanilines are toxic compounds known to inhibit nitrification and carbon removal in sludge bioreactors 43 , affecting both bacterial community structure and assembly 26 . Here, we expanded on it by doubling the organic loading as a different type of disturbance for a distinct microbial community inoculum, a relevant scenario given the multidimensional nature of disturbance 8 .…”

Section: Discussionmentioning

confidence: 99%

Microbiome assembly predictably shapes diversity across a range of disturbance frequencies in experimental microcosms

npj Biofilms Microbiomes

Wuertz

2022

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Diversity is often implied to have a positive effect on the functional stability of ecological communities. However, its relationship with stochastic and deterministic assembly mechanisms remains largely unknown, particularly under fluctuating disturbances. Here, we subjected complex bacterial communities in microcosms to different frequencies of alteration in substrate feeding scheme, tracking temporal dynamics in their assembly, structure and function. Activated sludge bioreactors were subjected to six different frequencies of double organic loading, either never (undisturbed), every 8, 6, 4, or 2 days (intermediately disturbed), or every day (press disturbed), and operated in daily cycles for 42 days. Null modeling revealed a stronger role of stochastic assembly at intermediate disturbance frequencies, with a peak in stochasticity that preceded the occurrence of a peak in α-diversity. Communities at extreme ends of the disturbance range had the lowest α-diversity and highest within-treatment similarity in terms of β-diversity, with stronger deterministic assembly. Increased carbon removal and microbial aggregate settleability (general functions) correlated with stronger deterministic processes. In contrast, higher stochasticity correlated with higher nitrogen removal (a specialized function) only during initial successional stages at intermediate disturbance frequencies. We show that changes in assembly processes predictably precede changes in diversity under a gradient of disturbance frequencies, advancing our understanding of the mechanisms behind disturbance–diversity–function relationships.