Isolation and Characterization of a Yellow Xanthophyll Pigment-Producing Marine Bacterium, Erythrobacter sp. SDW2 Strain, in Coastal Seawater

Xanthophylls, a yellow pigment belonging to the carotenoid family, have attracted much attention for industrial applications due to their versatile nature. We report the isolation of a homo xanthophyll pigment-producing marine bacterium, identified as the Erythrobacter sp. SDW2 strain, from coastal seawater. The isolated Erythrobacter sp. SDW2 strain can produce 263 ± 12.9 mg/L (89.7 ± 5.4 mg/g dry cell weight) of yellow xanthophyll pigment from 5 g/L of glucose. Moreover, the xanthophyll pigment produced by the SDW2 strain exhibits remarkable antioxidative activities, confirmed by the DPPH (73.4 ± 1.4%) and ABTS (84.9 ± 0.7%) assays. These results suggest that the yellow xanthophyll pigment-producing Erythrobacter sp. SDW2 strain could be a promising industrial microorganism for producing marine-derived bioactive compounds with potential for foods, cosmetics, and pharmaceuticals.

Influence of the total concentration and the profile of volatile fatty acids on polyhydroxyalkanoates (PHA) production by mixed microbial cultures

Polyhydroxyalkanoates (PHAs) production from lignocellulosic biomass using mixed microbial cultures (MMC) is a potential cheap alternative for reducing the use of petroleum-based plastics. In this study, an MMC adapted to acidogenic effluent from dark fermentation (DF) of exhausted sugar beet cossettes (ESBC) has been tested in order to determine its capability to produce PHAs from nine different synthetic mixtures of volatile fatty acids (VFAs). The tests consisted of mixtures of acetic, propionic, butyric, and valeric acids in the range of 1.5–9.0 g/L of total acidity and with three different valeric:butyric ratios (10:1, 1:1, and 1:10). Experimental results have shown a consistent preference of the MMC for the butyric and valeric acids as carbon source instead other shorter acids (propionic or acetic) in terms of PHA production yield (estimated in dry cell weight basis), with a maximum value of 23% w/w. Additionally, valeric-rich mixtures have demonstrated to carry out a fast degradation process but with poor final PHA production compared with high butyric mixtures. Finally, high initial butyric and valeric concentrations (1.1 g/L and 4.1 g/L) have demonstrated to be counterproductive to PHA production.

Overexpression of Shinorhizobium Meliloti Flavohemoglobinefficiently Improved Cell Growth and Fatty Acid Biosynthesis in Oleaginous Fungus Mucor Circinelloides

Oxygen availability is a limiting factor for lipid biosynthesis in eukaryotic microorganisms. Two bacterial hemoglobins from Vitreoscilla sp. (VHb) and Shinorhizobium meliloti (SHb), which could deliver the oxygen to the respiratory chain to produce more ATP, were introduced into Mucor circinelloides to alleviate oxygen limitation, thereby improving cell growth and fatty acid production. VHb and SHb genes were integrated into the M. circinelloides MU402 genome through homologous recombination, and their protein expression was verified by carbon monoxide difference spectrum (CO-difference spectrum)analysis. SHb-expressing strain showed higher biomass than VHb-expressing strain. The biomass of the SHb-expressing strain was increased by about 50% and the total fatty acid (TFA) content was as high as 15.7% of the dry cell weight which was about 40% higher than that of the control strain in flask conditions. In the fermenter, the maximum biomass and TFA content was obtained in SHb-expressing strains, with the biomass being 12.1 g/L and the TFA being 21.1% of the dry cell weight. VHb and SHb expression also affected the fatty acid composition with the proportion of polyunsaturated fatty acids being increased. Over-expression of bacterial hemoglobins, especially SHb increased cell growth and TFA content in M. circinelloides at low and high aeration, suggesting that SHb is better than VHb in improving the fatty acid production in oleaginous microorganisms.

The impact of carbon source on cell growth and the production of bioactive compounds in cell suspensions of Hancornia speciosa Gomes

Belonging to the Brazilian flora, the species Hancornia speciosa (Gomes), known as mangabeira, has bioactive compounds of interest, such as flavonoids, xanthones, and proanthocyanidins. The objective of this study was to determine how the supplementation of sugars in culture medium affects the osmotic potential of the medium, as well as its influence on cell growth and on the concentration of phenolic compounds. For this purpose, after 90 days of subculture, 20 mL aliquots of the cultures were added to flasks containing 20 mL of medium with different sugars (glucose, fructose, sucrose, mannitol, and sorbitol) under a 16-h photoperiod with a spectral range between 400 and 700 nm of photosynthetically active radiation (45–55 μmol m−2 s−1) in a shaker at 110 rpm. After 30 days, the pH, electrical conductivity, osmotic potential, biomass accumulation, and concentrations of phenolic compounds were evaluated. Regardless of their concentration in the medium, the sugars sorbitol and mannitol provided more unfavorable conditions for water absorption at the cellular level, reducing the water potential of the medium. Sucrose favored greater water absorption and biomass accumulation. Among the various sugar concentrations, 3% (30 g/L) sucrose or glucose improved the accumulation of fresh and dry cell weight and the production of polyphenols such as chlorogenic acid, epicatechin, rosmarinic acid, hesperidin, rutin, and quercetin. In addition, they resulted in a higher osmotic potential of the medium and larger cells than other carbon sources. Despite the differences in cell size, no culture conditions compromised cell survival.

Rapid and concise quantification of mycelial growth by microscopic image intensity model and application to mass cultivation of fungi

The microbial food fermentation industry requires real-time monitoring and accurate quantification of cells. However, filamentous fungi are difficult to quantify as they have complex cell types such as pellet, spores, and dispersed hyphae. In this study, numerous data of microscopic image intensity (MII) were used to develop a simple and accurate quantification method of Cordyceps mycelium. The dry cell weight (DCW) of the sample collected during the fermentation was measured. In addition, the intensity values were obtained through the ImageJ program after converting the microscopic images. The prediction model obtained by analyzing the correlation between MII and DCW was evaluated through a simple linear regression method and found to be statistically significant (R2 = 0.941, p < 0.001). In addition, validation with randomly selected samples showed significant accuracy, thus, this model is expected to be used as a valuable tool for predicting and quantifying fungal growth in various industries.

The synthesis of polyhydroxyalkanoates from low carbon wastewater under anaerobic-microaerobic process: effects of pH and nitrogen and phosphorus limitation

Polyhydroxyalkanoate (PHA) is a new type of bio-polyester which is expected to replace traditional petroleum-based plastics. The experiment was carried out based on anaerobic-microaerobic process. Firstly, the PHA accumulation capacity of activated sludge under different pH conditions was discussed, and then the batch test of nitrogen and phosphorus limitation was carried out under the condition of optimal pH. Moreover, the content of PHA monomer under nutrient restriction was also studied. The experimental results showed that when pH was not controlled (7.5~8.5), C:N and C:P weight ratio was equal to 150, the maximum content of PHA accounted for 50.39% and 36.07% of the dry cell weight, respectively. Besides, it was found that increasing the C:N weight ratio was beneficial to increasing the proportion of polyhydroxyvalerate (PHV) monomer in PHA.

Raw Glycerol Based Medium for DHA and Lipids Production, Using the Marine Heterotrophic Microalga Crypthecodinium cohnii

Crude glycerol, a biodiesel industry byproduct, and corn steep liquor (CSL) derived from a starch industry, were used as carbon and nitrogen sources, respectively, for lipid production, using the heterotrophic microalga C. cohnii grown in a bench bioreactor, in a batch culture. The maximum biomass concentration, lipid content and lipid productivity attained were 5.34 g/L, 24.6% (w/w Dry Cell Weight-DCW) and 0.016 g L−1 h−1, respectively. Flow cytometry analysis was used to evaluate the impact of these substrates on the microalgae cells. A high proportion of intact cells with enzymatic (esterases) activity (>50%) was present throughout the cultivation time course. These results indicate that crude glycerol and CSL can be used in the medium formulation for DHA and lipid production using this microalga, which reduce the process costs in an expected maximum of 84%.

The Recovery and Synthesis of Polyhydroxyalkanoates in the Process of Nitrogen and Phosphorus Removal in Low-Carbon Sewage Based on pH and Nitrogen and Phosphorus Restriction Under Anaerobic-Oxygen Limited Process

Polyhydroxyalkanoate (PHA) is a new type of bio-polyester which is expected to replace traditional petroleum-based plastics. It is also a critical transformation hub of carbon source in nitrogen and phosphorus removal in sewage. Based on the anaerobic-oxygen limited process, the experiment took organic solid waste fermentation liquid as carbon source control hub and realized PHA synthesis and recovery in denitrification and phosphorus removal from low carbon sewage the SBR reactor by regulating pH value and nitrogen and phosphorus restriction. The experimental results showed that when the ratio of C/N and C/P was 150, the content of PHA accounted for 50.39% and 36.07 of the dry cell weight, respectively. Besides, it was found that increasing the C/N ratio was beneficial to increasing the proportion of PHV in PHA. This study proved the feasibility of using an anaerobic-oxygen limited process to recover PHA in nitrogen and phosphorus removal from low-carbon sewage, which saves gas and reduces energy consumption. At the same time, it also provides some help for the follow-up study of low-carbon urban sewage nitrogen and phosphorus removal coupled with resource recovery of PHA to guide the water industry economy to develop in a circular and sustainable direction

Callus inducement of Toona sinensis: Potential agents against SARS-Corona virus replication

Bioprospecting of anti-SARS-corona virus phytochemical agents is an important issue today as an alternative to chemical drugs whose effectiveness has not been fully successful with no light effect. Quercetin, a component of Toona sinensis young leaves extract, was reported to have anti-viral activity against SARS-corona virus replication in vitro. Currently, the low efficiency of secondary metabolite production is an obstacle. Production of secondary metabolites from callus induction in vitro is considered more efficient and in a short time for commercial applications. The composition of hormones in callus media affects the secondary metabolites formed. The study was conducted to determine the effect of synthetic hormones auxin (BAP) and cytokinin (NAA) on callus percentage, fresh and dry callus cell weight and the average time of callus formation. The call percentage (100%) was obtained in different combinations of BAP and NAA in MS medium. The highest fresh weight of callus (165.50 gL−1) and dry cell weight (28.47 gL−1) were observed in MS medium (1.5 mgL−1 BAP and 1 mgL−1 NAA) within 7 days initial formation time of callus. The results showed that all the indices measured were positively correlated with callus induction in T. sinensis.

Harnessing molasses as a low-cost carbon source for production of poly-hydroxy butyrate (PHB) using Burkholderia sp. B73 bacteria

Burkholderia sp. has been reported as a poly-hydroxy-butyrate (PHB) producer. PHB is a natural polyester class with a wide range of applications in foods, medicines, and biomedicines. However, the high production cost of PHB may limit its potential. Molasses, a by-product of the sugarcane industry available abundantly, may be used as an alternative carbon source of PHB production. In this research, we aimed to evaluate PHB production by Burkholderia sp. B73 in fermentation media using molasses as an alternative carbon source. Small-scale experiments were performed in Erlenmeyer flasks on a shaker at 150 rpm and 30 °C to evaluate the best initial C/N ratio for biomass accumulation and PHB production. A set of parameters including bacterial growth, dry cell weight, yield, and FTIR spectrum of PHB were observed. The results showed that molasses could be used to grow Burkholderia sp. B73 and the highest PHB production was obtained when a 20:1 C/N ratio of molasses was applied in the fermentation medium. In addition, when the initial pH was adjusted to 7.0, the highest PHB yield was also produced. More importantly, the use of molasses as a carbon source improved the PHB yield by nearly 2-fold compared with our previous report using a synthetic Ramsay’s minimal medium. In conclusion, the experiment results showed that molasses could be used as a low-cost carbon source for PHB production by Burkholderia sp. B73 bacteria.