Biology subjects

Alloul, A.

Publications and source records attributed to Alloul, A..

3 recordsLinked to original sources

bioRxiv2020

Purple bacteria as added-value protein ingredient in shrimp feed: Litopenaeus vannamei growth performance, and tolerance against Vibrio and ammonia stress

Purple non-sulfur bacteria (PNSB) biomass is an emerging alternative protein source, yet research of PNSB as added-value protein ingredient is limited. This research aimed to study the use of PNSB as protein source for shrimp and investigate the shrimps tolerance against Vibrio and ammonia stress. A 28-day shrimp feeding trial was performed with Rhodopseudomonas palustris, Rhodobacter capsulatus and a mixed PNSB culture. PNSB contained in feed (5-10% protein substitution) resulted in 5-26% higher individual weights, better feed conversions ratios (1.2-1.7) compared to commercial feed (1.7) and tolerance against ammonia. In parallel, the effect of PNSB on the growth of Vibrio pathogens was tested in vitro. The species Rps. palustris, Rb. capsulatus, Rb. sphaeroides, Rhodospirillum rubrum and Afifella marina suppressed the growth of Vibrio parahaemolyticus TW01 and V. campbellii LMG 21363. Overall, this study demonstrated the potential of PNSB as nutritious feed ingredient for shrimp. This can contribute to circular economy, as PNSB enable resource recovery from wastewater. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/964007v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@13773acorg.highwire.dtl.DTLVardef@18b24e7org.highwire.dtl.DTLVardef@23df69org.highwire.dtl.DTLVardef@1208e93_HPS_FORMAT_FIGEXP M_FIG Graphical abstract C_FIG HighlightsO_LIPurple non-sulfur bacteria (PNSB) enhance the growth performance of shrimp C_LIO_LIPNSB-fed shrimp has better feed conversion ratio, growth rate and weight gain C_LIO_LIShrimp fed with Rhodopseudomonas are more resistance against ammonia stress C_LIO_LIFreeze-dried and live PNSB inhibit Vibrio pathogens in vitro C_LI

bioengineering↗

bioRxiv2020

Control tools to selectively produce purple bacteria for microbial protein in raceway reactors

Purple non-sulfur bacteria (PNSB) show potential for microbial protein production on wastewater as animal feed. They offer good selectivity (i.e. uneven community with high abundance of one species) when grown anaerobically in the light. However, the cost of a closed anaerobic photobioreactor (PBR) is prohibitive for protein production. While open raceway reactors are cheaper, their feasibility to selectively grow PNSB is thus far unexplored. This study developed tools to boost PNSB abundance in the biomass of a raceway reactor fed with volatile fatty acids as carbon source. For oxygen availability as tool, not stirring in the night (i.e. reduced oxygen supply) elevated the PNSB abundance from 8% to 20%. For light availability as tool, a 24-h illumination increased the PNSB abundance from 8% to 31% compared to a 12-h light/12-h dark regime. A reactor run at 2-d sludge retention time at the highest surface-to-volume ratio (10 m2 m-3 increased light availability) showed productivities up to 0.2 g protein L-1 d-1 and the highest PNSB abundance (78%). The estimated production cost is {euro}1.9 kg-1 dry weight (vs. PBR {euro}11.4 kg-1 dry weight). This study pioneered in PNSB-based microbial protein production in raceways, yielding cost efficiency along with high selectivity when avoiding the combined availability of oxygen, COD and darkness. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/912980v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@c5e3borg.highwire.dtl.DTLVardef@1fe8d28org.highwire.dtl.DTLVardef@e5630borg.highwire.dtl.DTLVardef@1c99bf3_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2020

Enriching and aggregating purple non-sulfur bacteria in an anaerobic sequencing-batch photobioreactor for nutrient capture from wastewater

Purple non-sulfur bacteria (PNSB), a guild of anoxygenic photomixotrophic organisms, rise interest to capture nutrients from wastewater in mixed-culture bioprocesses. One challenge targets the aggregation of PNSB biomass through gravitational separation from the treated water to facilitate its retention and accumulation, while avoiding the need for membranes. We aimed to produce an enriched, concentrated, well-settling, nutrient-removing PNSB biomass using sequencing batch regimes (SBR) in an anaerobic photobioreactor. The stirred tank was fed with a synthetic influent mimicking loaded municipal wastewater (430-860 mg CODAc LInf-1, COD:N:P ratio of 100:36:4-100:11:2 m/m/m), operated at 30{degrees}C and pH 7, and continuously irradiated with infrared (IR) light (>700 nm) at 375 W m-2. After inoculation with activated sludge at 0.1 g VSS L-1, PNSB were rapidly enriched in a first batch of 24 h: the genus Rhodobacter reached 54% of amplicon sequencing read counts. SBR operations at volume exchange ratio of 50% with decreasing hydraulic retention times (48 to 16 h; 1 to 3 cycles d-1) and increasing volumetric organic loading rates (0.2 to 1.3 kg COD m-3 d-1) stimulated the aggregation (compact granules of 50-150 m), settling (sedimentation G-flux of 4.7 kg h-1 m-2), and accumulation (as high as 3.8 g VSS L-1) of biomass. The sludge retention time (SRT) increased freely from 2.5 to 11 d without controlled sludge wasting. Acetate, ammonium, and orthophosphate were removed simultaneously (up to 96% at a rate of 1.1 kg COD m-3 d-1, 77% at 113 g N m-3 d-1, and 73% at 15 g P m-3 d-1) with a COD:N:P assimilation ratio of 100:6.7:0.9 (m/m/m). Competition for substrate and photons occurred in the PNSB guild. SBR regime shifts sequentially selected for Rhodobacter (90%) under shorter SRT and non-limiting acetate concentrations during reaction phases, Rhodopseudomonas (70%) under longer SRT and acetate limitation, and Blastochloris (10%) under higher biomass concentrations. We highlighted the benefits of a PNSB-based SBR process for biomass accumulation and simultaneous nutrient capture at substantial rates, and its underlying microbial ecology. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/899062v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1f167bdorg.highwire.dtl.DTLVardef@1d1c1e2org.highwire.dtl.DTLVardef@fe591org.highwire.dtl.DTLVardef@1a8c4e3_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIPNSB were highly enriched (90%) in an anaerobic stirred-tank photobioreactor. C_LIO_LIThe mixed-culture SBR process fostered PNSB biomass aggregation and accumulation. C_LIO_LIPNSB sludge reached 3.8 g VSS L-1 and a sedimentation G-flux of 4.7 kg h-1 m-2. C_LIO_LIPNSB enabled a high simultaneous removal of COD (96%), N (77%), and P (73%). C_LIO_LIRhodobacter, Rhodopseudomonas, and Blastochloris competed for acetate and photons. C_LI

bioengineering↗