Biology subjects

Vethathirri, R. S.

Publications and source records attributed to Vethathirri, R. S..

6 recordsLinked to original sources

bioRxiv2026

Dual-loop involving microbial single-cell protein production from soybean-processing wastewater and effluent-based refinement for circular bioeconomy applications

Nutrient-rich food-processing wastewaters represent valuable yet under-utilised side streams for sustainable protein production in the form of microbial biomass. Here we present an integrated dual-loop bioprocess that converts soybean-processing wastewater into microbial single-cell protein (SCP) while achieving substantial nutrient removal and product refinement. In the first loop, previously enriched microbial consortia were inoculated and cultivated in four parallel sequencing batch reactors (SBRs) for 44Ldays at a hydraulic retention time (HRT) of 3Ldays. This bioprocess configuration demonstrated features that support future scale-up while maintaining process stability, achieving a protein content of 33.3L{+/-}L3.2%, doubling the protein yield (15.32L{+/-}L3.49Lg dry weight per g soluble TKN) and quadrupling the production rate (0.29L{+/-}L0.06Lg dry weight LL{superscript 1} dL{superscript 1}) compared to operating reactors without inoculation (HRT: 7.2Ldays). Effluent treatment was stable, with 84% carbon and 78% nitrogen removal efficiencies, demonstrating efficient nutrient recovery. The SCP biomass was enriched in functional taxa, including Acidipropionibacterium, Lactococcus, Megasphaera, and Azospirillum, suggesting that reactor conditions and inoculum selection promoted a stable, protein-productive microbial community with potential probiotic benefits. In the second loop, bioreactor effluent was reused as aqueous matrix for heat treatment (60{degrees}C) of the SCP biomass, reducing the RNA content from 8.6% to 2.6%, with a 39% biomass loss accompanied by a 30% increase in total amino acid concentration. Hence, our valorisation approach integrates microbial biomass production, effluent reuse, and product refinement within a circular framework. The system provides a resource-efficient pathway for converting food-sector side streams into high-quality microbial community-based SCP, highlighting its potential scalability for sustainable nutrient and water management.

microbiology↗

bioRxiv2026

Microbial community-based single-cell protein supports partial fishmeal replacement in juvenile Asian seabass diets across feeding trials and production scales

The growing demand for sustainable aquafeeds has intensified interest in alternative protein ingredients capable of reducing reliance on fishmeal without compromising fish performance. Here, we evaluated microbial community-based single-cell protein (SCP) as a fishmeal substitute in juvenile Asian seabass (Lates calcarifer) diets in two independent feeding trials of juvenile fish conducted over 49 and 56 days, respectively and compared them to a previous study that lasted 24 days. SCP was produced from nutrient-rich soybean-processing side streams by microbial communities in fermenters and incorporated into experimental diets at inclusion levels ranging from 10% to 100% fishmeal replacement. In the 24-day trial, a diet containing 50% fishmeal replacement with lab-scale produced SCP achieved 100% survival and a feed conversion ratio (FCR), specific growth rate (SGR), and weight gain comparable to the fishmeal control diet. In the 49-day trial using pilot-scale produced SCP, a 50% fishmeal replacement also maintained an FCR and feed intake comparable to the control, whereas complete replacement reduced feed intake and growth performance. In a 56-day pilot-scale trial that used 500-L fish tanks, diets containing up to 50% fishmeal replacement maintained comparable survival, weight gain, and SGR, although moderately higher FCR values were observed at higher SCP inclusion levels. Proximate composition and essential amino acid profiles of fish fed control or SCP-containing diets were comparable. Genome-resolved metagenomic analyses revealed diverse microbial taxa associated with the SCP. Collectively, these findings support microbial community-based SCP as a scalable and reproducible alternative protein platform for aquaculture feeds across independent trials and production scales.

microbiology↗

bioRxiv2026

Growth-resolved genome-scale metabolic modeling of Priestia megaterium SR7 validated by chemostat and 13-C flux analysis

Priestia megaterium SR7 is a promising candidate chassis for bioprocess engineering, but its development is limited by the availability of condition-grounded, mechanistic models that can translate experimental measurements into predictive design hypotheses. Here, we present PMSR7, a genome-scale metabolic model for SR7, and evaluate it under a growth-resolved chemostat framework spanning a dilution-rate series. Stable steady states were established across the growth regime, with the highest dilution rate (D = 1.1538 h-{superscript 1}) excluded from growth interpretation due to biomass collapse. Extracellular carbon fluxes were quantified by NMR and reported as mean {+/-} SD, providing an experimental basis for model comparison. PMSR7 was benchmarked using MEMOTE against representative reference reconstructions, supporting structural consistency suitable for constraint-based analyses. Under growth-resolved simulations, ATP demand scaled linearly with growth rate, enabling inference of maintenance-energy behavior across the regime. Growth-dependent feasibility and magnitude of overflow secretion were evaluated for acetate, lactate, and formate using feasible-space analyses, highlighting both agreement and regime-sensitive limitations. Finally, growth-resolved leucine and valine production was assessed in both raw and fold-change space, with experimental means compared against median-based summaries of sampled model distributions to account for feasible-space skew. Together, these results establish PMSR7 as a reproducible, quality-benchmarked platform for SR7 chassis development and provide a framework for iterative experimental integration in non-model organisms, where the dominant challenge is achieving congruence between measured physiology and model-feasible behavior.

systems biology↗

bioRxiv2025

Microbial community-based protein enables sustainable fishmeal replacement and improved resilience in Pacific white shrimp (Litopenaeus vannamei)

The growing demand for aquaculture feeds requires sustainable alternatives to fishmeal. Microbial community-based single-cell protein (SCP) produced from soybean-processing wastewater offers a circular approach that combines nutrient recovery with aquafeed production. We evaluated SCP as a fishmeal replacement for Pacific white shrimp (Litopenaeus vannamei) across four feeding trials lasting 42-84 days, involving shrimp from different hatcheries and SCP produced at laboratory and pilot scales. Diets containing 0-100% fishmeal replacement, corresponding to up to 220 g SCP kg-1 feed, were tested. Replacement of 50% was consistently supported across trials, while levels up to 90% maintained several key performance outcomes, including specific growth rate, feed conversion ratio, and survival, without significant differences from the fishmeal control. Complete replacement reduced growth in one trial, potentially reflecting the lower protein content and less favourable amino acid balance of SCP relative to fishmeal, particularly its lower lysine and methionine proportions. Shrimp tissue proximate and amino acid compositions showed no clear adverse responses to SCP inclusion in the trial in which they were assessed. Cross-trial analysis revealed a positive association between SCP replacement and survival after accounting for trial-specific baseline differences, with survival increasing by an estimated 1.53 percentage points for every 10-percentage-point increase in replacement (HC3 95% CI: 0.90-2.17; P < 0.001). Although the mechanisms underlying this association remain to be established, the findings support investigation of potential functional effects through targeted challenge and mechanistic studies. Overall, performance across four heterogeneous trials supports substantial fishmeal replacement by microbial community-based SCP and demonstrates its potential for practical application as a circular aquafeed ingredient.

microbiology↗

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↗