Rhodovulum sulfidophilum in the treatment and utilization of sardine processing wastewater

Purple non-sulfur bacteria technology: a promising and potential approach for wastewater treatment and bioresources recovery

Shortage of water, energy, and bioresources in the world has led to the exploration of new technologies that achieve resource recovery from wastewater, which has become a new sustainable trend. Photosynthetic non-sulfur bacteria (PNSB), the most ancient photo microorganism, not only treats different wastewater types, but also generates PNSB cells, which are non-toxic bioresources and containing many value-added products. These bioresources can be used as raw materials in the agricultural, food, and medical industries. Therefore, PNSB or PNSB-based wastewater resource recovery technology can be simultaneously used to treat wastewater and produce useful bioresources. Compared with traditional wastewater treatment, this technology can reduce CO₂ emissions, promote the N recovery ratio and prevent residual sludge disposal or generation. After being developed for over half a century, PNSB wastewater resource recovery technology is currently extended towards industrial applications. Here, this technology is comprehensively introduced in terms of (1) PNSB characteristics and metabolism; (2) PNSB wastewater treatment and bioresource recovery efficiency; (3) the relative factors influencing the performance of this technology, including light, oxygen, strains, wastewater types, hydraulic retention time, on wastewater treatment, and resource production; (4) PNSB value-added bioresources and their generation from wastewater; (5) the scale-up history of PNSB technology; (6) Finally, the future perspectives and challenges of this technology were also analysed and summarised.

Protein recovery as a resource from waste specifically via membrane technology-from waste to wonder

Economic growth and the rapid increase in the world population has led to a greater need for natural resources, which in turn, has put pressure on said resources along with the environment. Water, food, and energy, among other resources, pose a huge challenge. Numerous essential resources, including organic substances and valuable nutrients, can be found in wastewater, and these could be recovered with efficient technologies. Protein recovery from waste streams can provide an alternative resource that could be utilized as animal feed. Membrane separation, adsorption, and microbe-assisted protein recovery have been proposed as technologies that could be used for the aforementioned protein recovery. This present study focuses on the applicability of different technologies for protein recovery from different wastewaters. Membrane technology has been proven to be efficient for the effective concentration of proteins from waste sources. The main emphasis of the present short communication is to explore the possible strategies that could be utilized to recover or restore proteins from different wastewater sources. The presented study emphasizes the applicability of the recovery of proteins from various waste sources using membranes and the combination of the membrane process. Future research should focus on novel technologies that can help in the efficient extraction of these high-value compounds from wastes. Lastly, this short communication will evaluate the possibility of integrating membrane technology. This study will discuss the important proteins present in different industrial waste streams, such as those of potatoes, poultry, dairy, seafood and alfalfa, and the possible state of the art technologies for the recovery of these valuable proteins from the wastewater.

A marine photosynthetic microbial cell factory as a platform for spider silk production

Photosynthetic microorganisms such as cyanobacteria, purple bacteria and microalgae have attracted great interest as promising platforms for economical and sustainable production of bioenergy, biochemicals, and biopolymers. Here, we demonstrate heterotrophic production of spider dragline silk proteins, major ampullate spidroins (MaSp), in a marine photosynthetic purple bacterium, Rhodovulum sulfidophilum, under both photoheterotrophic and photoautotrophic growth conditions. Spider silk is a biodegradable and biocompatible material with remarkable mechanical properties. R. sulfidophilum grow by utilizing abundant and renewable nonfood bioresources such as seawater, sunlight, and gaseous CO₂ and N₂, thus making this photosynthetic microbial cell factory a promising green and sustainable production platform for proteins and biopolymers, including spider silks.

Foong et al. demonstrate production of spider dragline silk proteins in Rhodovulum sulfidophilum, a marine photosynthetic purple bacterium. This platform generates promise for the sustainable production of valuable biocompounds in photosynthetic organisms.

Photosynthetic bacteria-based technology is a potential alternative to meet sustainable wastewater treatment requirement?

A paradigm shift is underway in wastewater treatment from pollution removal to resource or energy recovery. However, conventional activated sludge (CAS) as the core technology of wastewater treatment is confronted with severe challenges on high energy consumption, sludge disposal and inevitable greenhouse gas emission, which are posing a serious impact on the current wastewater industry. It is urgent to find new alternative methods to remedy these defects. Photosynthetic bacteria (PSB) have flexible metabolic modes and high tolerance, which enhance the removal of nutrients, heavy metals and organic contaminants efficiency in different wastewater. The unique phototrophic growth of PSB breaks the restriction of nutrient metabolism in the CAS system. Recent studies have shown that PSB-based technologies can not only achieve the recovery of nutrient and energy, but also improve the degradation efficiency of refractory substances. If the application parameters can be determined, there will be great prospects and economic effects. This review summarizes the research breakthroughs and application promotion of PSB-based wastewater treatment technology in recent years. Comparing discussed the superiority and inferiority from the perspective of application range, performance differences and recovery possibility. Pathways involved in the nutrient substance and the corresponding influencing parameters are also described in detail. The mode of PSB biodegradation processes presented a promising alternative for new wastewater treatment scheme. In the future, more mechanical and model studies, deterministic operating parameters, revolutionary process design is need for large-scale industrial promotion of PSB-based wastewater treatment.

Production of single cell protein from manure as animal feed by using photosynthetic bacteria

To reduce the cost of protein feedstock for animal feed, the use of single cell protein (SCP) produced from waste of animal agriculture is an interesting choice. This study reveals that chicken manure was the best substrate for SCP production by submerged fermentation using photosynthetic bacteria compared to swine, cow, and buffalo manure. Regression analysis showed that the productions were found to be significantly influenced by chicken manure content, inoculum size, and cultivation time. Response surface methodology based on central composite design generated the optimal condition (15% chicken manure, 30% inoculum size and cultivation time for 14 days) at which biomass, protein, and carotenoid productions were increased by 92.3%, 21.6%, and 18.2%, respectively. The percentage of error between the predicted and actual values for biomass, protein, and carotenoid productions were 1.56%, 2.64%, and 2.09%, respectively, which indicates the precision of the model. To verify the quality of SCP, the bacterium was cultured in a photobioreactor to investigate amino acid composition, protein, and nucleic acid contents. The SCP yielded 62.7% protein with essential amino acids including lysine, methionine, threonine, phenylalanine, leucine, isoleucine, valine, histidine, and low nucleic acid content of 4.52%. This study suggests an alternative SCP production for animal feed as well as the strategy for animal waste management.

Bio-conversion of photosynthetic bacteria from non-toxic wastewater to realize wastewater treatment and bioresource recovery: A review

Generating or recycling water and resources from wastewater other than just treating wastewater is one of the most popular trends worldwide. Photosynthetic bacteria (PSB) wastewater treatment and resource recovery technology is one of the most potential methods. PSBs are non-toxic and contain lots of value-added products that can be utilized in the agricultural and food industries. They are effective to degrade pollutants and synthesize useful biomass, thus realizing wastewater treatment, bioresource production, and eliminating waste sludge. If all the nutrients in wastewaters could be bio-converted by PSB, then pollutant reductions and economic benefits would be achieved. This review paper firstly describes and summarizes this technology, including PSBs classification, metabolism, and the market application. The feasibility, technical procedures, bioreactors, pollutant removal, and bioresource production are also summarized, compared and evaluated. Issues that concern the advantages and industrialization of this technologies at the plant scale are also discussed.

One-step treatment and resource recovery of high-concentration non-toxic organic wastewater by photosynthetic bacteria

In order to achieve simple pollutant removal and simultaneous resource recovery in high-COD-non-toxic wastewater treatment, a one-step photosynthetic bacteria (PSB) method was established using batch study experiment. The effluent COD met the national discharge standard, and biomass with rich protein and high-value substances was efficiently produced. It eliminated the demand of post-treatment for conventional PSB treatment. Results showed that Rhodopseudomonas effectively treated brewery wastewater and achieved biomass proliferation. Yeast extract was the best additive for PSB growth and the effluent COD was below 80 mg/L with 400 mg/L yeast extract, meeting the national discharge standard. In addition, the PSB biomass increased by 2.6 times, and the cells were rich in protein, polysaccharide, carotenoids, bacteriochlorophyll and coenzyme Q10, reaching 420.9, 177.6, 2.53, 10.75 and 38.6 mg/g respectively. This work demonstrated the great potential of PSB for high-COD non-toxic wastewater treatment in one-step process.

A novel PSB-EDI system for high ammonia wastewater treatment, biomass production and nitrogen resource recovery: PSB system

A novel process coupling photosynthetic bacteria (PSB) with electrodeionization (EDI) treatment was proposed to treat high ammonia wastewater and recover bio-resources and nitrogen. The first stage (PSB treatment) was used to degrade organic pollutants and accumulate biomass, while the second stage (EDI) was for nitrogen removal and recovery. The first stage was the focus in this study. The results showed that using PSB to transform organic pollutants in wastewater into biomass was practical. PSB could acclimatize to wastewater with a chemical oxygen demand (COD) of 2,300 mg/L and an ammonia nitrogen (NH4(+)-N) concentration of 288-4,600 mg/L. The suitable pH was 6.0-9.0, the average COD removal reached 80%, and the biomass increased by an average of 9.16 times. The wastewater COD removal was independent of the NH4(+)-N concentration. Moreover, the PSB functioned effectively when the inoculum size was only 10 mg/L. The PSB-treated wastewater was then further handled in an EDI system. More than 90% of the NH4(+)-N was removed from the wastewater and condensed in the concentrate, which could be used to produce nitrogen fertilizer. In the whole system, the average NH4(+)-N removal was 94%, and the average NH4(+)-N condensing ratio was 10.0.

Comparison between freeze and spray drying to obtain powder Rubrivivax gelatinosus biomass

The use of colorants in products of animal origin is justified by the improvement in the color of foods since this attribute is considered a quality criterion. These additives can be produced using industrial effluents as substrates and appropriate organisms, such as Rubrivivax gelatinosus. Oxycarotenoids represent a class of carotenes responsible for the pigmentation of animals and vegetables. R. gelatinosus grows in fish industry effluent with the resulting production of a bacterial biomass containing oxycarotenoids. The purpose of this study was to compare the use of two drying processes - spray and freeze drying - to obtain powder biomass in terms of the process parameters (yield, productivity, and product recovery) and the product characteristics (color, proximate composition, and oxycarotenoids). No difference was detected in the yield between these techniques, while productivity was higher using spray drying. Higher product recovery and moisture were achieved with freeze drying, while ash was higher with spray drying. The freeze dried biomass was redder, darker and less saturated than the spray dried biomass. No difference in oxycarotenoids was detected between the biomasses. Although it results in lower recovery rate, spray drying was faster and more productive, and it provided the same yield as freeze drying, which makes it the method of choice for obtaining R. gelatinosus biomass.

Phototrophic growth of Rubrivivax gelatinosus in poultry slaughterhouse wastewater

Rubrivivax gelatinosus was grown in Pfennig's synthetic medium (PM) and in treated wastewater from poultry slaughterhouse (TW) to assess growth profiles for biomass production. Cultures inoculated at 1% (v/v) were grown under anaerobiosis at 30+/-2 degrees C and 1400+/-200 lux for 12 days. Regular absorbance curves for R. gelatinosus were found both on PM and TW. On PM, the highest dry weight of biomass, 0.39 gL(-1), was achieved in the 216-h culture and the highest specific growth rate of 0.2960 h(-1) occurred in the 24-h culture. On TW, the highest biomass of 0.57 gL(-1) was also obtained in the 216-h culture and the highest specific growth rate, 0.1970 h(-1), was achieved in the 48-h culture. For productivity and chemical oxygen demand investigations, the cultivation was accomplished in the TW under anaerobiosis at 32+/-2 degrees C and 4000+/-500 lux, for 10 days. Productivity was 0.085 g biomass (d.w.) L(-1) day(-1), with a COD decrease of 91%.