Biology subjects

Hoon, H. Y.

Publications and source records attributed to Hoon, H. Y..

3 recordsLinked to original sources

bioRxiv2023

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

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 genera Acidipropionibacterium and Propioniciclava, 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.

microbiology↗

bioRxiv2022

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

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 {square} 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.

microbiology↗

bioRxiv2021

Global warming readiness: Feasibility of enhanced biological phosphorus removal from wastewater at 35oC

Recent research has shown enhanced biological phosphorus removal (EBPR) from municipal wastewater at warmer temperatures around 30{degrees}C to be stable in both laboratory-scale reactors and full-scale treatment plants. In the context of a changing climate, the feasibility of EBPR at even higher temperatures is of interest. We operated two lab-scale EBPR sequencing batch reactors with alternating anaerobic and aerobic phases for over 300 days at 30{degrees}C and 35{degrees}C, respectively, and followed the dynamics of the communities of phosphorus accumulating organisms (PAOs) and competing glycogen accumulating organisms (GAOs) using a combination of 16S rRNA gene metabarcoding, quantitative PCR and fluorescent in-situ hybridization analyses. Stable and nearly complete P removal was achieved at 30{degrees}C; similarly, long term P removal was stable at 35{degrees}C with effluent PO43--P concentrations < 0.5 mg/L on half of all monitored days. Diverse and abundant Ca. Accumulibacter amplicon sequence variants were closely related to those found in temperate environments, suggesting that EBPR at this temperature does not require a highly specialized PAO community. The slow-feeding strategy used effectively limited the carbon uptake rates of GAOs, allowing PAOs to outcompete GAOs at both temperatures. Candidatus Competibacter was the main GAO, along with cluster III Defluviicoccus members. These organisms withstood the slow-feeding regime, suggesting that their bioenergetic characteristics of carbon uptake differ from those of their tetrad-forming relatives. This specific lineage of GAOs warrants further study to establish how complete P removal can be maintained. Comparative cycle studies at two temperatures for each reactor revealed higher activity of Ca. Accumulibacter when the temperature was increased from 30{degrees}C to 35{degrees}C, suggesting that the stress was a result of the higher carbon (and/or P) metabolic rates of PAOs and GAOs, the resultant carbon deficiency, and additional community competition. An increase in the TOC to PO43--P ratio (from 25:1 to 40:1) effectively eased the carbon deficiency and benefited the proliferation of PAOs. In general, the slow-feeding strategy and sufficiently high carbon input benefited a high and stable EBPR at elevated temperature and represent basic conditions for full-scale applications.

microbiology↗