Continuous valorization of food waste and oily food waste using bacteria-pumice and bacteria-smectite nanocomposites: Alternative cell immobilization and zooplankton lifespan impact.

Recycling waste into commercial products is a profitable strategy but the lifetime of immobilized cells for long-term waste treatment remains a problem. This study presents alternative cell immobilization methods for valorizing food waste (FW) and oily food waste (OFW) to microbial carotenoids and proteins. Carriers (pumice or smectite), magnetite nanoparticles, and isolated photosynthetic bacteria were integrated to obtain magnetically recoverable bacteria-pumice and bacteria-smectite nanocomposites. After recycling five batches (50 d), chemical oxygen demand removal from FW reached 76% and 78% with the bacteria-pumice and bacteria-smectite nanocomposite treatments, respectively, and oil degradation in OFW reached 71% and 62%, respectively. Destructive changes did not occur, suggesting the durability of nanocomposites. The used nanocomposites had no impact on the lifespan of Moina macrocopa or water quality as assessed by toxicity analysis. Bacteria-pumice and bacteria-smectite nanocomposites are efficient for food waste recycling and do not require secondary treatment before being discharged into the environment.

Alternative microbial-based functional ingredient source for lycopene, beta-carotene, and polyunsaturated fatty acids.

The acquisition of carotenoids and polyunsaturated fatty acids (PUFAs) from plants and animals for use as functional ingredients raises concerns regarding productivity and cost; utilization of microorganisms as alternative sources is an option. We proposed to evaluate the production of carotenoids and PUFAs by Rhodopseudomonas faecalis PA2 using different vegetable oils (rice bran oil, palm oil, coconut oil, and soybean oil) as carbon source, different concentrations of yeast extract as nitrogen source at different cultivation time to ensure the best production. Cultivation with soybean oil as source of carbon led to the most significant changes in the fatty acid profile. Compared to the initial condition, the strain cultivated in the optimal conditions (4% soybean oil, 0.35% yeast extract, and 14 days of incubation) showed an increase in µmax, biomass, carotenoid productivity, and microbial lipids by 102.5%, 52.7%, 33.82%, and 34.78%, respectively. The unsaturated fatty acids content was raised with additional types of PUFAs; omega-3 [alpha-linolenic acid and eicosapentaenoic acid] and omega-6 [linoleic acid and eicosatrienoic acid] fatty acids were identified. The results of ultra high-performance liquid chromatography-electrospray ionization-quadrupole time of flight-mass spectrometry (UHPLC-ESI-QTOF-MS/MS) indicated the molecular formula and mass of bacterial metabolites were identical to those of lycopene and beta-carotene. The untargeted metabolomics revealed functional lipids and several physiologically bioactive compounds. The outcome provides scientific reference regarding carotenoids, PUFAs, and useful metabolites that have not yet been reported in the species Rhodopseudomonas faecalis for further use as a microbial-based functional ingredient.

Photosynthetic bacteria with iron oxide nanoparticles as catalyst for cooking oil removal and valuable products recovery with heavy metal co-contamination.

Waste cooking oil discharge causes environmental pollution in receiving waters, particularly when associated with heavy metals that can lead to formation of hazardous organometallic compounds. This study combined iron oxide nanomaterial and the anoxygenic photosynthetic bacterium Rhodopseudomonas faecalis PA2 for removal of cooking oil in the presence of heavy metals. R. faecalis PA2, with known capability to generate beneficial substances from several wastes, was capable of cooking oil removal with production of valuable products. Oil removal, biomass, protein, and carotenoid production were 82.38%, 1.48 g/L, 1,600.19 mg/L, and 1,046.33 mg/L, respectively, under optimal conditions (cooking oil as carbon source and 30% inoculum density). Iron (Fe) stimulates growth of R. faecalis; in this study, Fe3O4 nanoparticles were synthesized and used as a catalyst to facilitate interaction and high reactivity between Fe and R. faecalis PA2. Size measurement by transmission electron microscopy (17.44 nm), X-ray diffraction peaks, and magnetic susceptibility confirmed that the synthesized nanoparticles were magnetite Fe3O4. Biomass, protein, and carotenoid production of the Fe3O4 supplemented experiment increased by 61.56%, 70.78%, and 57.2%, respectively, when compared with the control. When different concentrations of heavy metals (Pb, Ni, Co, and Zn) were supplemented in the media containing cooking oil, Fe3O4 addition increased heavy metal tolerance, improved bacterial growth, and enhanced valuable products when compared with the non-supplemented group. This study reports the positive impact of nanoparticle application as a catalyst for valorization of cooking oil waste with heavy metal co-contamination by the photosynthetic bacterium R. faecalis PA2.

Single-phase and two-phase cultivations using different light regimes to improve production of valuable substances in the anoxygenic photosynthetic bacterium Rhodopseudomonas faecalis PA2.

This study aimed to improve biomass, carotenoid, bacteriochlorophyll, protein, lipid, and carbohydrate contents of Rhodopseudomonas faecalis PA2 using different light regimes. Light intensity (4000, 6000, 8000, and 10,000 lx), together with photoperiod (24:0, 16:8, 12:12, and 8:16 h light/dark), was assigned as single-phase (SP) cultivation while two-phase (TP) cultivation used two light intensities (using 4000 lx as the first phase), together with the control of phase shift (3, 6, and 9 days) and photoperiod. Biomass, carotenoid, and bacteriochlorophyll contents were maximized by SP cultivation; light at 8000 lx with light-dark cycle of 24:0 was optimal for pigments synthesis. In contrast, TP was useful to enhance storage compounds; protein, lipid, and carbohydrate productivities were significantly increased by 121.69%, 101.69%, and 92.44%, respectively, in TP when compared with SP. This indicates that the novel light strategy proposed in this study was able to manipulate the production of valuable substances in this strain.

Recycling of sugar industry wastewater for single-cell protein production with supplemental carotenoids.

The bioconversion of sugar-industry wastewater to value-added products is a prominent topic in biotechnology. This work cultured a carotenoid-producing photosynthetic bacterium, Rhodopseudomonas faecalis, in a photo-bioreactor containing different wastewater from wastewater treatment ponds of a Thai sugar company. The cultivated R. faecalis produced single cell protein (SCP) with supplemental carotenoids. The cultivation boosted the growth and dehydrogenase activity of R. faecalis from all wastewater sources, while significantly reducing the total sugar concentration. The cellular protein concentration and carotenoid production of R. faecalis was maximised in wastewater collected from anaerobic pond and secondary mechanically aerated pond, respectively. At the end of the cultivation, the chemical oxygen demand was reduced by 80% and the protein content in the dry biomass exceeded 50%, within the acceptable ranges of SCP production. The biomass contained all essential amino acids and the leucine and lysine proportions were above the SCP guideline values. This study reveals that sugar-industry wastewater can be recycled in SCP production with supplemental carotenoids. The SCP is a potential commercial product for the sugar industry.

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.

Biomass recovery during municipal wastewater treatment using photosynthetic bacteria and prospect of production of single cell protein for feedstuff.

Utilization of photosynthetic bacteria (PSB) for wastewater treatment and production of biomass for economical single cell protein production is a feasible option. In this study, Rhodopseudomonas sp. CSK01 was used for municipal wastewater treatment and the effect of initial pH, light intensity and additional carbon source was investigated. Optimum chemical oxygen demand (COD) removal and biomass production were achieved when the initial pH and light intensity were 7 and 4000 lux, respectively. The specific growth rate, biomass yield and biomass productivity were found to be 0.4/d, 3.2 g/g COD and 2.1 g/L/d, respectively, which were improved by 100%, 167% and 200% relative to the original condition. Under the optimal conditions, COD removal reached 85% and maximum biomass was 6.2 g/L accomplished within three days of cultivation. The biomass had a relatively high protein content (60.1%) consisting of all essential amino acids. The contents of histidine, lysine, phenylalanine and leucine were superior to those of the previously described PSB. Results showed that COD removal was not improved in the presence of additional carbon sources (glucose, sucrose and malic acid). The addition of malic acid significantly increased the biomass accumulation by 279% relative to the original condition, whereas COD removal was declined due to carbon catabolite repression. In this study, PSB biomass recovery and catabolite repression are proposed in municipal wastewater treatment by Rhodopseudomonas sp.