Growth Of Purple Nonsulfur Bacteria Research Articles

Outdoor biohydrogen production by thermotolerant Rhodopseudomonas pentothenatexigens KKU-SN1/1 in a cluster of ten bioreactors system.

In tropical regions, the viability of outdoor photo-fermentative biohydrogen production faces challenges arising from elevated temperatures and varying light intensity. This research aimed to explore how high temperatures and outdoor environments impact both biohydrogen production and the growth of purple non-sulfur bacteria. Our findings revealed the potential of Rhodopseudomonas spp. as a robust outdoor hydrogen-producing bacteria, demonstrating its capacity to thrive and generate biohydrogen even at 40°C and under fluctuating outdoor conditions. Rhodopseudomonas harwoodiae NM3/1-2 produced the highest cumulative biohydrogen of 223mL/L under anaerobic light conditions at 40°C, while Rhodopseudomonas harwoodiae 2M had the highest dry cell weight of 2.93g/L. However, R. harwoodiae NM3/1-2 demonstrated the highest dry cell weight of 3.99g/L and Rhodopseudomonas pentothenatexigens KKU-SN1/1 exhibited the highest cumulative biohydrogen production of 400mL/L when grown outdoors. In addition, the outdoor enhancement of biohydrogen production was achieved through the utilization of a cluster of ten bioreactors system. The outcomes demonstrated a notable improvement in biohydrogen production efficiency, marked by the highest daily biohydrogen production of 493mL/Ld by R. pentothenatexigens KKU-SN1/1. Significantly, the highest biohydrogen production rate was noted to be 17 times greater than that observed in conventional batch production methods. This study is the first to utilize R. pentothenatexigens and R. harwoodiae for sustained biohydrogen production at high temperatures and in outdoor conditions over an extended operational period. The successful utilization of a clustered system of ten bioreactors demonstrates potential to scale-up for industrial biohydrogen production.

An Experimentally Evaluated Thermodynamic Approach to Estimate Growth of Photoheterotrophic Purple Non-sulfur Bacteria.

Distribution of energy during the growth and formation of useful chemicals by microorganisms can define the overall performance of a biotechnological system. However, to date, this distribution has not been used to reliably predict growth characteristics of phototrophic microorganisms. The presented research addresses this application by estimating the photon-associated Gibbs energy delivered for the photoheterotrophic growth of purple non-sulfur bacteria and production of dihydrogen. The approach is successfully evaluated with the data from a fed-batch growth of Rhodopseudomonas palustris nifA∗ fixing N2 gas in phototrophic conditions and a reliable prediction of growth characteristics is demonstrated. Additionally, literature-available experimental data is collected and used for evaluation of the presented thermodynamic approach to predict photoheterotrophic growth yields. A proposed thermodynamic framework with modification to account for the phototrophic growth can be used to predict growth rates in broader environmental niches and to assess the possibility for the development of novel biotechnological applications in light-induced biological systems.

Photoheterotrophic growth of purple non-sulfur bacteria on Tris Acetate Phosphate Yeast extract (TAPY) medium and its hydrogen productivity in light under nitrogen deprivation

In this study, an active photoheterotrophic growth of purple non-sulfur bacteria (PNSB) on Tris Acetate Phosphate Yeast extract (TAPY) medium is reported. TAPY medium is a modified TAP medium supplemented with filter sterilized yeast extract (0.3 g L−1) and vitamin B12. Heterotrophic growth of PNSB on nitrogen replete TAPY medium in dark could be obtained but much slower than that in light where cells could grow but without formation of pigments. The medium showed high potency for hydrogen production under nitrogen deprivation in light by Rhodobacter sphaeroides DSM 5864. Through using TAPY medium, 1 mole of acetate provided as glacial acetic acid produced 0.819 mole of hydrogen gas by R. sphaeroides on nitrogen deprived TAPY medium (initial pH 7 adjusted by HCl) with a maximum H2 production rate of (0.669 mmol H2 h−1 L−1) obtained at 42 h after start of fermentation. Repeated-batch hydrogen production could be achieved with high efficiency for three cycles by supplementing the nitrogen deprived culture with filter sterilized sodium acetate at the end of the log hydrogen production phase of each cycle. The medium was also applicable for photoheterotrophic growth in light and heterotrophic growth in dark of other PNSB namely Rhodobacter capsulatus JCM-21090 and Rhodospirillum rubrum DSM 467. Although R. rubrum could actively grow on TAPY medium under nitrogen deprivation in light, it was the lowest in hydrogen production compared to R. sphaeroides and R. capsulatus. The active growth of R. rubrum on nitrogen deprived TAPY medium suggests its possible use for producing biodegradable plastic polymers better than hydrogen. The results suggest that it's possible to use TAPY medium for growth and producing variable bioproducts by PNSB in future studies and applications. The repeated-batch hydrogen production by R. sphaeroides on nitrogen deprived TAPY medium is promising for large-scale applications of hydrogen production industry by only sequential supply with sodium acetate to the culture for three rounds of batch fermentation. This is the first report in using TAPY medium for growth and hydrogen production by PNSB.

Long-term performance and operational strategies of a poultry slaughterhouse waste stabilization pond system in a tropical climate

This paper discusses the performance of a poultry slaughterhouse wastewater treatment plant (WWTP) in a tropical country and operating strategies that were applied over 84 months to this WWTP. The WWTP consisted of a dissolved air flotation (DAF) system, anaerobic ponds (APs) and a facultative pond (FP). The organic loading rates applied to the APs ranged from 0.26 to 1.05kgBOD/m3day, and the hydraulic retention time ranged from 2.2 to 3.8days. The resultant COD and BOD removal efficiencies were 42±11% and 38±15%, respectively. The FP surface loading was up to 983kgBOD/haday. The main observed events in the WWTP processes over this period were organic overload, low chemical oxygen demand (COD) and biochemical oxygen demand (BOD) removal efficiencies and color change from green to reddish at the FP. Molecular biology techniques were used to identify microbial groups in the FP in the period of low organic matter removal efficiency and when the liquid became reddish. Sunny conditions favored anoxygenic photosynthesis, the growth of purple nonsulfur bacteria (such as Rhodocyclales-like organisms), and green nonsulfur bacteria (such as Chloroflexi-like organisms). Mechanical aeration at the inlet of the FP restored the water to its original color and increased the COD and BOD removal efficiencies. Based on the BOD removal efficiencies of 89%, after the installation of aerators, the operating strategies illustrate the WWTP system's capacity and versatility to adapt to load variations.

Bacterial co-existence system to alleviate sulfide inhibition of growth of purple nonsulfur bacteria in a resource-recovery process from wastewater

Bacterial co-existence system to alleviate sulfide inhibition of growth of purple nonsulfur bacteria in a resource-recovery process from wastewater

Optimization of wastewater feeding for single-cell protein production in an anaerobic wastewater treatment process utilizing purple non-sulfur bacteria in mixed culture condition

Impacts of operation timing of feeding and withdrawal on anaerobic wastewater treatment utilizing purple non-sulfur bacteria have been investigated in mixed culture condition with acidogenic bacteria. Simulated wastewater containing glucose was treated in a laboratory-scale chemostat reactor, changing the timing of wastewater feeding and withdrawal. Rhodopseudomonas palustris, which does not utilize glucose as a substrate, was inoculated in the reactor. Rps. palustris was detected by a fluorescent in situ hybridization (FISH) technique using the specific Rpal686 probe. As a result, population ratios of Rps. palustris were over 20% through the operation. Rps. palustris could grow by utilizing metabolites of acidogenic bacteria that coexisted in the reactor. A morning feed was effective for a good growth of purple non-sulfur bacteria. A protein content of cultured bacteria was the highest when wastewater was fed in the morning. Dissolved organic carbon (DOC) removal was 94% independent of the timing control. Consequently, feeding in the morning is the optimum feed-timing control from the aspects of growth of purple non-sulfur bacteria and single-cell protein production.

Aeration Conditions Affecting Growth of Purple Nonsulfur Bacteria in an Organic Wastewater Treatment Process

Effects of aeration on purple nonsulfur bacteria (PnSB) were studied in photobioreactors. Bacterial community changes were analyzed by denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH). DGGE band pattern change was small and only few prominent bands were obtained at non-aeration condition. Sequencing results of the prominent DGGE bands obtained at this condition revealed that they represented mainly the PnSB, Rhodobacter sphaeroides and Rhodopseudomonas palustris. On the other hand, under aerated condition, some prominent bands originated from heterotrophs appeared but no proliferation of PnSB was observed. FISH was applied to detect PnSB and their population was quantified. Maximum PnSB ratio (up to 80%) was obtained both at non-aeration condition and at constant ORPs less than -200 mV. In the presence of DO, Rps. palustris was more competitive to chemoheterotrophs than Rb. sphaeroides.