Maximum Dry Cell Weight Research Articles

Polyhydroxybutyrate (PHB)-Based sustainable bioplastic derived from Bacillus sp. KE4 isolated from kitchen waste effluent

Petrochemical-derived plastics pose a major threat to the biosphere and the environment due to their acute or long-term toxicity. Therefore, to ensure sustainability, it is essential to find an effective replacement for synthetic plastics with natural and ecofriendly biomaterial. In this context, production of polyhydroxybutyrate (PHB) was produced by the Bacillus sp. KE4 using glucose as the carbon source, and a maximum dry cell weight (DCW) of 4.4 g/l with a PHB concentration of 3.1 g/l, PHB yield of 0.15 g/g was obtained, and the PHB content was 70.4% of the DCW. The extracted biopolymer was characterized using FTIR, GC-MS, 1H NMR, and 13C NMR which confirmed the structure of the biopolymer as PHB. The findings of TGA, DTG, DTA and DSC studies corresponded to PHB's excellent thermal stability. PHB biopolymer has a melting temperature of 168.7 °C and a maximum degradation temperature of 273 °C. The weight average molar mass (Mw), number average molar mass (Mn), and polydispersity index (PDI) of the extracted PHB was 1,55,436 g mol−1; 1,43,258 g mol−1; and 1.08, respectively. The XRD analysis validated the material's partly crystalline nature. FESEM-EDS and XPS were employed to determine the elemental composition of the purified PHB film. The Young's modulus, tensile strength and elongation at break showed rigid and brittle nature of PHB. Using open windrow composting method, the extracted PHB biopolymer film was assessed to determine its biodegradability. Within 28 days of soil burial, it was found that the biopolymer film had degraded by 61.34%. Cytotoxicity assessment in HepG2 cells indicated that PHB is non-cytotoxic in nature. The results have showed that the biomaterial is environmentally benign, biodegradable, and biocompatible; therefore, it may find its diverse application covering packaging, medicine, agriculture and allied fields.

Heavy toxic sludge tolerance in microalgae: Effect of energy generation metabolisms from C. humicola under IAA applications

Industrial sludge is characterized by high moisture content, complex composition, and significant organic toxicity. This research aimed to improve the performance of Chlorococcum humicola in removing hydroquinone-domesticated sludge toxicity through the addition of indole-3-acetic acid (IAA). The maximum cell density and dry weight of C. humicola were attained when the IAA concentration was 5.0 × 10−6 mol/L, at 6.79 × 107 cells/mL and 2.60 g/L, respectively. The toxicity of the sludge degradation rate reached its peak level of 59.70% on the 20th day. The toxicity reduction was consistent with the decrease of RNA degradation-related proteins such as A5FN12, which can be hydrolyzed and absorbed by C. humicola via active transport. In the presence of IAA, C. humicola increased its energy production processes, such as glycolysis and oxidative phosphorylation, to facilitate active transport. Moreover, the efficiency of signal transduction was improved, leading to enhanced cellular metabolism. The suppression of biosynthesis of glutathione and arginine at the molecular level may contribute to this observed trend. Overall, this study provides new insights into the mechanism by which IAA promotes the degradation of sludge toxicity by C. humicola, offering a novel method and theoretical basis for the safe and resource-based utilization of industrial sludge.

The efficient capture of polysaccharides in Tetradesmus obliquus of indole-3-acetic acid coupling sludge extraction

Polysaccharide is an important biomass of algae. The sludge extract is rich in organic substances, which can be used by algae for biomass growth and high-value biomass synthesis, but its organic toxicity has an inhibitory effect on algae. To overcome inhibition and improve polysaccharide enrichment, Tetradesmus obliquus was cultured with sludge extract with different indole-3-acetic acid (IAA) concentrations. Within 30 days of the culture cycle, T. obliquus showed in good condition at the IAA dosage content of 10−6 M, the maximum cell density and dry weight were respectively (106.78 ± 2.20) × 106 cell/mL and 2.941 ± 0.067 g/L while the contents of chlorophyll-a, chlorophyll-b, and carotenoid were 1.79, 1.91 and 2.80 times that of the blank group, respectively. The highest polysaccharide accumulation was obtained under this culture condition, reaching 533.15 ± 21.11 mg/L on the 30th day, which was 2.49 times that in the blank group. By FT-IR and NMR analysis, it was found that the polysaccharides of T. obliquus were sulfated polysaccharide with glucose and rhamnose as the main monosaccharides. Proteomic showed that the up-regulation of A0A383WL26 and A0A383WLM8 enhanced the light trapping ability, and A0A383WMJ2 enhanced the accumulation of NADPH. The up-regulation of A0A383WHD5 and A0A383WAY6 indicated that IAA culture could repair the damage caused by sludge toxicity, thus promoting the accumulation of biomass. The above findings provided new insights into the mechanism of sludge toxicity removal of T. obliquus and the enhancement of the polysaccharide accumulation effect under different concentrations of IAA.

Fed-batch cultivation of Euglena gracilis for the high-yield production and GPC-assisted molecular weight determination of paramylon.

Paramylon, a starch-like carbohydrate accumulated in Euglena gracilis cells, could be a potential source as a raw material for chemical products; its high-yield production would thus be highly desired. Although the molecular weight and polymerization degree of paramylon are important properties for its use as a raw material for chemical products, the available information about paramylon molecular weight remains insufficient. Therefore, in this study, we investigated a high-density E. gracilis culture approach and how culture conditions affect paramylon molecular weight. The nitrogen source, cultivation temperature, and nutrient feeding were optimized for maximum biomass and paramylon productivity. The maximum dry cell weight and paramylon content yields reached 108.9g/L and 87.2%, respectively. Paramylon molecular weight was in the range of 220000-320000Da. Our gel permeation chromatography analysis showed that the cells with a higher paramylon content tended to contain paramylon of a higher molecular weight.

Sugar cane bagasse hydrolysate (SBH) as a lucrative carbon supplement to upgrade the lipid and fatty acid production in Chlorococcum sp. for biodiesel through an optimized binary solvent system

Cost is the crucial impediment in commercializing microalgal biodiesel. Therefore, cultivating microalgae in cost-effective nutrients reduces the upstream process cost remarkably. Thus, in this study, sugar cane bagasse hydrolysate (SBH) as a lucrative carbon supplement for Chlorococcum sp. and subsequent lipid extraction via an optimized solvent system for biodiesel production was investigated. Characterization of SBH revealed the presence of various monosaccharides and other sugar derivatives such as glucose, fructose, xylose, arabinose, etc. The maximum dry cell weight of 1.7 g/L was estimated in cultures grown in 10 mL SBH. Different solvents such as diethyl ether (DEE), chloroform (CHL), ethyl acetate (ETA), hexane (HEX), methanol (MET), ethanol (ETOH), acetone (ACE) and also combination of solvents (2:1 ratio) such as DEE: MET, CHL: MET, HEX: MET, HEX: ETOH was tested for lipid extraction efficacy. Among solvents used, 12.3% and 18.4% of lipids were extracted using CHL and CHL: MET, respectively, from 10 mL SBH amended cultures. However, the biodiesel yield was found to be similar at about 70.16 % in both SBH and no SBH-added cultures. The fatty acid profile of the biodiesel shows palmitic, oleic, linoleic, linolenic, and arachidonic acid as principal fatty acids. Further, the levels of SFAs, MUFAs, and PUFAs in 10 mL SBH-added cells were 24.67, 12.89, and 34.24%, respectively. Eventually, the fuel properties of Chlorococcum sp. biodiesel, satisfying international biodiesel standards, make the biodiesel a viable diesel substitute in the future.

Production of poly (3-hydroxybutyrate) and extracellular polymeric substances from glycerol by the acidophile Acidiphilium cryptum.

Acidiphilium cryptum is an acidophilic, heterotrophic, and metallotolerant bacteria able to use dissolved oxygen or Fe(III) as an electron sink. The ability of this extremophile to accumulate poly(3-hydroxybutyrate) (PHB) and secrete extracellular polymeric substances (EPS) has also been reported. Hence, the aim of this work is to characterize the production of PHB and EPS by the wild strain DSM2389 using glycerol in shaken flasks and bioreactor. Results showed that maximum PHB accumulation (37-42% w/w) was obtained using glycerol concentrations of 9 and 15gL-1, where maximum dry cell weight titers reached 3.6 and 3.9gL-1, respectively. The culture in the bioreactor showed that PHB accumulation takes place under oxygen limitation, while the redox potential of the culture medium could be used for online monitoring of the PHB production. Recovered EPS was analyzed by Fourier-transform infrared spectroscopy and subjected to gas chromatography-mass spectrometry after cleavage and derivatization steps. These analyses showed the presence of sugars which were identified as mannose, rhamnose and glucose, in a proportion near to 3.2:2.3:1, respectively. Since glycerol had not been used in previous works, these findings suggest the potential of A. cryptum to produce biopolymers from this compound at a large scale with a low risk of microbial contamination due to the low pH of the fermentation process.

Comparison of different aerobic sludge on enriching polyhydroxyalkanoate mixed microbial culture using lactic acid fermentation broth of agricultural wastes

Lactic acid fermentation broth derived from pig manure and apple waste is a potential high-quality feedstock for production of the biodegradable plastic polyhydroxyalkanoate (PHA). Enrichment of active PHA-synthesizing bacterial consortia, namely mixed microbial culture (MMC), is an important factor in high-efficiency synthesis of PHA. In this study, two types of aerobic sludge (pig farm sludge and municipal sludge) were selected to acquire active MMCs in the enrichment process with sludge retention times of 2 and 8 days using the lactic acid fermentation broth. Batch reactors and PHA accumulation reactors were used to evaluate the MMC activity. Results showed that pig farm sludge was acclimated to the superior MMC with the maximum PHA content of 25% during the enrichment process with sludge retention time of 8 days. The structure of microbial communities in all treatments tended to be similar after 45 days’ enrichment, and the dominant bacteria were genus Paracoccus with abundance of 15.41–41.45%. The maximum dry cell weight, PHA content, and PHA yield of batch reactors using the superior MMC were 0.69 g/L, 36%, and 0.86 g PHA-COD/g COD, respectively. Dry cell weight concentrations reached 3.16 g/L in the PHA accumulation reactor with PHA content of 40–50% and PHA yield of 0.57 g PHA-COD/ g COD. The findings of this study provide an effective enrichment strategy for MMCs, which could improve the high efficiency synthesis of PHA from the fermentation broth of agricultural wastes and enhance the economy of PHA production at a marketable scale.

Optimization of Biomass Cultivation from Tuber borchii and Effect of Additives on Triterpenoid Production

Edible fungi are renowned for producing biologically active secondary metabolites that possess anti-tumor activity, protect the liver and have other benefits. The cultivation of truffle mycelia through submerged fermentation has gained interest in the production of metabolites for bio-medicinal purposes. In the present study, Tuber borchii was cultivated by submerged fermentation to produce both biomass and triterpenoids. Various additives, including palmitic acid, stearic acid, linoleic acid, chitosan, CaCl2 and limonene, were investigated to enhance triterpenoid production. It was observed that increasing the medium’s linoleic acid concentration to 1 g/L increased the production of triterpenoids to 129.29 ± 6.5 mg/L, which was 2.94 times higher than the control. A number of variables, including potassium and magnesium ion concentrations and carbon and nitrogen sources and concentrations, were considered to ascertain the ideal conditions for T. borchii growth in submerged fermentation. The best concentrations for glucose, yeast extract, peptone, malt extract, KH2PO4 and MgSO4·7H2O in submerged fermentation were 19.45, 4.58, 7.91, 5.3, 0.58 and 0.82 g/L, respectively, according to response surface methodology. Validation analysis revealed that the experimental values and the predicted values were in good agreement. Under ideal circumstances, the maximum dry cell weight (2.980.18 g/L), which was 1.39 times greater than the control, was attained. Finally, the addition of 1.5 g/L linoleic acid on day 14 to the optimal medium elevated the triterpenoid production to 212.63 ± 16.58 mg/L, which was a 4.84-fold increase compared to the control.

Regulatory mechanism of high-concentration CO2 on polysaccharide accumulation in Tetradesmus obliquus cultured in sludge extract

Microalgae such as Tetradesmus obliquus have great potential in immobilizing high-concentration CO2 and removing highly toxic organic matters, which could be produced from coal chemical industry and coal chemical wastewater biological treatment process. In this study, Tetradesmus obliquus was cultured in sludge extract and high-concentration CO2 was added. The maximum cell density and dry weight were respectively (111.46 ± 4.87) × 106 cell/mL and 3.365 ± 0.168g/L under 30% CO2. Tetradesmus obliquus accumulated the most polysaccharides (629.60 ± 31.48mg/L) on the 30th day under 30% CO2. The results of proteomic showed that the upregulation of A0A2Z4THB7 and A0A383VAT1 promoted polysaccharide accumulation. Polysaccharide was mainly formed at the stable phase instead of the log-growth phase due to the abiotic stress caused by high TOC at the log-growth phase. Collectively, this study revealed the regulatory mechanism of high-concentration CO2 on the toxicity removal and accumulation of polysaccharides in Tetradesmus obliquus.

Cultivation of Arthrospira platensis and harvesting using edible fungi isolated from mould soybean cake

In this study, the cultivation and harvesting of Arthrospira platensis biomass were proposed via simple, safe, and efficient techniques for direct consumption. Cultivation of microalgae in a covered macrobubble column under outdoor conditions resulted in significant differences (p < 0.05) with a maximum dry cell weight (Xm) of 0.959 ± 0.046 g/L. Notably, outdoor cultures resulted in approximately twofold biomass compared to indoor cultures. This outcome shows that the developed outdoor setup integrated with solar panels while utilising Malaysia's weather and atmospheric air as carbon sources is viable. Meanwhile, for harvesting, the screening showed that the fungus isolated from mould soybean cake (tempeh) starter indicated the highest harvesting efficiency, which was then further identified as Rhizopus microsporus, microscopically and molecularly. Overall, the economical and portable setup of outdoor cultivation coupled with safe harvesting via locally isolated fungus from tempeh as a bioflocculant would provide sustainability to produce A. platensis biomass.

The comprehensive impact of phosphorus sources on microalgae biochemical metabolism and phosphorus transformation

Understanding the comprehensive impact of phosphorus sources on microalgae growth process is an essential precondition for microalgae cultivation. In this study, the combination of inorganic phosphorus (K2HPO4 and Na5P3O10) and organic phosphorus (ATP and G6P) on microalgae biochemical metabolism and phosphorus transformation with wastewater was clarified. Both inorganic phosphorus (IP) and organic phosphorus (OP) could be absorbed and utilized by Chlorella pyrenoidosa under mixotrophic condition. The maximum dry cell weight was obtained with K2HPO4 and ATP at an IP/OP proportion of 1:3, which was 1.04, 1.09 and 1.30 times higher than K2HPO4 and G6P, Na5P3O10 and ATP, Na5P3O10 and G6P, respectively. The increasing proportion of OP was advantageous for microalgae growth, but disadvantageous for lipid accumulation. Besides, the intracellular phosphorus was classified and quantified by 31P NMR spectroscopy to ascertain its metabolism and transformation. Results provided a fresh perspective on the utilization of complex phosphorus sources with microalgae.

Agriculture of microalgae Chlorella vulgaris for polyunsaturated fatty acids (PUFAs) production employing palm oil mill effluents (POME) for future food, wastewater, and energy nexus

Malaysia is one of the second largest world palm oil exporters; correspondingly, the massive production of palm oil mill effluent (POME) is a significant concern. The present investigation aimed to isolate and characterize the potential microalgae and maximize the growth and biomass productivity of Chlorella sp. using POME. Chlorella vulgaris was cultured in BG-11 (control) and POME with 1:1, 1:2, 1:3, and 1:4 dilution ratios. Binary solvent extraction was applied to extract lipids, and polyunsaturated fatty acids (PUFAs) in the fatty acid methyl ethers were determined using gas chromatography coupled with mass spectrometry (GC-MS). Results suggest the lipid level of 21 wt.% was the highest amount obtained from biomass Chlorella vulgaris cultivated in 1:4 diluted POME. Chlorella sp. in POME with a 1:4 dilution ratio gives the highest biomass yield. It also yields the maximum dry cell weight of 0.42 g/L. Therefore, this study indicates that diluted POME with different dilutions is a suitable growth medium for Chlorella vulgaris biomass cultivation. Pairing wastewater with algae culture reduces biomass production and water treatment costs. Further studies demand more attention for future food, wastewater, and energy nexus.

β-glucosidase production by recombinant Pichia pastoris strain Y1433 under optimal feed profiles of fed-batch cultivation.

Pichia pastoris, a methylotrophic yeast, is known to be an efficient host for heterologous proteins production. In this study, a recombinant P. pastoris Y11430 was found better for β-glucosidase activity in comparison with a wild type P. pastoris Y11430 strain, and thereby, subjected to methanol intermittent feed profiling for β-glucosidase production. The results showed that at 72h of cultivation time, the cultures with 16.67% and 33.33% methanol feeding with constant rate could produce the total dry cell weight of 52.23 and 118.55g/L, respectively, while the total mutant β-glucosidase activities were 1001.59 and 3259.82 units, respectively. The methanol feeding profile was kept at 33% with three methanol feeding strategies such as constant feed rate, linear feed rate, and exponential feed rate which were used in fed-batch fermentation. At 60h of cultivation, the highest total mutant β-glucosidase activity was 2971.85 units for exponential feed rate culture. On the other hand, total mutant β-glucosidase activity of the constant feed rate culture and linear feed rate culture were 1682.25 and 1975.43 units, respectively. The kinetic parameters of exponential feed rate culture were specific growth rate on glycerol 0.228/h, specific growth of methanol 0.061/h, maximum total dry cell weight 196.73g, yield coefficient biomass per methanol ([Formula: see text]) 0.57 gcell/gMeOH, methanol consumption rate ([Formula: see text]) 5.76 gMeOH/h, and enzyme productivity ([Formula: see text]) 75.96 units/h. In conclusion, higher cell mass and β- glucosidase activity were produced under exponential feed rate than constant and linear feed rates.

Photo-fermentative hydrogen production from organic acids mixtures evaluated through predictive models for Rhodobacter capsulatus strains

This research aimed to evaluate growth and hydrogen production from Rhodobacter capsulatus DSM155 and B10 strains in function of volatile fatty acids (VFA) media composition, as well as to assess the light intensity effect on hydrogen production. The growth of DSM155 and B10 was verified in media containing either acetic acid, butyric acid, or sodium lactate, or a mixture of them (ABL medium), being the ABL medium that produced the maximum cell dry weight, 2.15 and 1.67 g/L for DSM155 and B10, respectively. Biohydrogen production was evaluated in media containing acetic and butyric acids (AB medium), and ABL medium. Both strains presented the highest hydrogen production using ABL medium, being the highest 239.2 mL H2 for DSM155. Finally, light intensity (10, 20, and 30 klux) effect on biohydrogen production was studied using the best strain and medium, i.e., DSM155 and ABL medium. DSM155 produced hydrogen increasingly in the order 10, 20, and 30 klx (2753.5, 2850.5, and 2946.3 mL H2/Lop, respectively); however, the light conversion efficiency into hydrogen showed an inverse trend, 7.47, 4.16, and 2.67 %. In conclusion, R. capsulatus DSM155 is advisable for biohydrogen production using ABL medium in the range 10-30 klux. Moreover, further work is recommended on DSM 155 using organic acid-rich real effluents from dark fermentation.

Fermenting and Lignin Degradability of a White-Rot Fungus Coriolopsis trogii Using Industrial Lignin as Substrate.

Bio-depolymerized the lignin macromolecules into low molecular lignin-derived aromatic compounds satisfies the requirement for carbon dioxide peaking and is also one of the important ways to realize lignin valorization. Coriolopsis trogii is a kind of less reported lignin-degrading white-rot fungus. The degradability of a self-isolated C. trogii TS01 on industrial lignins, including enzymatic hydrolysis lignin (EHL) and Kraft lignin (KL), was investigated in this paper. The results indicated that EHL could be used as an efficient carbon source to promote the cell growth and ligninolytic enzyme secretion of C. trogii TS01. Compared with using 2% glucose as carbon source, 1% EHL plus 1% glucose would increase the maximum cell dry weight, laccase activity, and manganese-dependent peroxidase activity of C. trogii TS01 by 24.8%, 164.1%, and 200%, respectively. However, the cell growth and ligninolytic enzyme secretion would be significantly inhibited in the case of 1% KL plus 1% glucose used as carbon source. As a result, at the 12th day of fermentation, the degradation rates of EHL and KL were 50.6% and 5.7%, respectively. The UV and FTIR analysis indicated that after been fermented by C. trogii TS01, S-unit content in EHL was decreased by 12.5% but G-unit content was increased by 53.7%. In conclusion, the research of this paper will provide a promising solution for the valorization of enzymatic hydrolysis lignin since the high biodegradation rate of lignin and high activity of ligninolytic enzymes could be achieved simultaneously.

Investigation of Hydrodynamic Parameters in an Airlift Photobioreactor on CO2 Biofixation by Spirulina sp.

The rise of CO2 concentration on Earth is a major environmental problem that causes global warming. To solve this issue, carbon capture and sequestration technologies are becoming more and more popular. Among them, cyanobacteria can efficiently sequestrate CO2, which is an eco-friendly and cost-effective way of reducing carbon dioxide, and algal biomass can be harvested as valuable products. In this study, the hydrodynamic parameters of an airlift photobioreactor such as gas holdup, mean bubble diameter and liquid circulation velocity were measured to investigate CO2 biofixation by Spirulina sp. The total gas holdup was found to increase linearly with the increase in the gas velocity from 0.185 to 1.936 cm/s. The mean bubble velocities in distilled water only and in the cyanobacterial culture on the first and sixth days of cultivation were 109.97, 87.98, and 65.89 cm/s, respectively. It was found that shear stress at gas velocities greater than 0.857 cm/s led to cyanobacterial death. After 7 days of batch culture, the maximum dry cell weight reached 1.62 g/L at the gas velocity of 0.524 cm/s, whereas the highest carbon dioxide removal efficiency by Spirulina sp. was 55.48% at a gas velocity of 0.185 cm/s, demonstrating that hydrodynamic parameters applied in this study were suitable to grow Spirulina sp. in the airlift photobioreactor and remove CO2.

Enhanced co-production of medium-chain-length polyhydroxyalkanoates and phenazines from crude glycerol by high cell density cultivation of Pseudomonas chlororaphis in membrane bioreactor

Enhanced co-production of medium-chain-length polyhydroxyalkanoates (mcl-PHA) and extracellular phenazines was assessed through a high cell density cultivation of Pseudomonas chlororaphis subsp. aurantiaca (DSM 19603) in a membrane bioreactor using crude glycerol as a fermentative substrate. A maximum dry cell weight (DCW) of 59.25 ± 0.31 g/L was achieved at 90 h of cultivation with a maximum mcl-PHA and extracellular phenazines concentrations of respectively 19.05 ± 0.04 g/L (32.16% of DCW) and 79.42 ± 0.35 mg/L. mcl-PHA concentration achieved through cell retention culture was 28.43-folds higher than that obtained by batch culture. Fourier transform infrared spectroscopy, gas chromatography–mass spectrometry, and 1H nuclear magnetic resonance analysis identified the produced PHA as a mcl-PHA copolymer of 3-hydroxyhexanoate (0.68%), 3-hydroxyoctanoate (7.76%), 3-hydroxydecanoate (49.18%), 3-hydroxydodecanoate (4.89%), and 3-hydroxytetradecanoate (37.50%). The mcl-PHA exhibited a highly amorphous structure with low crystallinity index (4.19%) and high thermal stability. This is the first report on the enhanced co-production of mcl-PHA and phenazines in a membrane bioreactor.

Supplementation with rac-GR24 Facilitates the Accumulation of Biomass and Astaxanthin in Two Successive Stages of Haematococcus pluvialis Cultivation.

The unicellular freshwater green alga Haematococcus pluvialis has attracted much research attention due to its biosynthetic ability for large amounts of astaxanthin, a blood-red ketocarotenoid that is used in cosmetics, nutraceuticals, and pharmaceuticals. Recently, numerous studies have investigated the functions of natural astaxanthin; however, the high cost of the production of astaxanthin from H. pluvialis cultures restricts its commercial viability. There is an urgent need to fulfill commercial demands by increasing astaxanthin accumulation from H. pluvialis cultures. In this study, we discovered that treatment of H. pluvialis cultures at the beginning of the macrozooid stage (day 0) with 1 μM rac-GR24, a synthetic analogue of strigolactones (a class of phytohormones), led to significant increases in biomass [up to a maximum dry cell weight (DCW) of 0.53 g/L] during the macrozooid stage and astaxanthin (from 0.63 to 5.32% of DCW) during the hematocyst stage. We elucidated that this enhancement of biomass accumulation during the macrozooid stage by rac-GR24 is due to its increasing CO2 utilization efficiency in photosynthesis and carbohydrate biosynthesis. We also found that rac-GR24 stimulated the overproduction of nicotinamide adenine dinucleotide phosphate (NADPH) and antioxidant enzymes in H. pluvialis cultures, which alleviated the oxidative damage caused by reactive oxygen species generated during the hematocyst stage due to the exhaustion of nitrogen supplies. Moreover, rac-GR24 treatment of H. pluvialis synergistically altered the activity of the pathways of fatty acid biosynthesis and astaxanthin esterification, which resulted in larger amounts of astaxanthin being generated by rac-GR24-treated cultures than by controls. In summary, we have developed a feasible and economic rac-GR24-assisted strategy that increases the amounts of biomass and astaxanthin generated by H. pluvialis cultures, and have provided novel insights into the mechanistic roles of rac-GR24 to achieve these effects.

Enhanced Production of Phenylethanoids Mediated Through Synergistic Approach of Precursor Feeding and Light Regime in Cell Suspension Culture of Rhodiola imbricata (Edgew.).

Precursor feeding is a potential strategy for increasing specialized metabolite production in plant cell culture systems. In the present study, cell suspension cultures were developed and subsequently evaluated for precursor feeding investigations. Cell suspension cultures were established in Murashige and Skoog (MS) medium containing 0.5mg/L thidiazuron (TDZ) + 1mg/L α-naphthalene acetic acid (NAA). The growth biomass and metabolite pattern were analyzed to identify specific culture days required for prolific biomass production. The maximum cell dry weight (DW) was observed in leaf cell suspension (1.22g/100mL) and root cell suspension culture (1.12g/100mL) on day 21. Afterward, the effect of precursor concentrations (tyrosol; 0.5, 1, 2, and 3mM) along with two light regimes, photoperiod (16L/8D h, 70µmol/m2/s) and dark (24h), was evaluated for cell growth and metabolite accumulation. The results revealed that leaf cell suspension treated with 3mM tyrosol concentration detected maximum salidroside content (26.05mg/g DW) on day 15, incubated under photoperiod (16L/8D h) condition. Similarly, under photoperiod (16L/8D h), root cell suspension treated with 3mM tyrosol produced maximum salidroside content (26.62mg/g DW) on day 12. Moreover, the total phenolics content increased significantly (44.21mg/g DW) on day 12 in 3mM tyrosol treatment under photoperiod (16L/8D h). However, precursor concentrations did not influence the total flavonoids content. The present investigation suggests that the immediate pathway precursor, tyrosol, has a strong effect on enhanced production of salidroside, irrespective of explant type and light regimes.

Metagenomics and network analysis elucidating the coordination between fermentative bacteria and microalgae in a novel bacterial-algal coupling reactor (BACR) for mariculture wastewater treatment

To achieve the goal of treating mariculture wastewater economically and efficiently, a novel bacterial-algal coupling reactor (BACR) integrating acidogenic fermentation and microalgae cultivation was firstly investigated for mariculture wastewater treatment. Volatile fatty acids (VFAs) generated in the dark chamber migrated into the photo chamber for microalgal utilization, which alleviated the pH drop and feedback inhibition of the acidogenic fermentation. The maximum dry cell weight (DCW) of microalgae was 1.46 g/L, and pollutants such as chemical oxygen demand (COD), ammonium (NH4+-N) and total phosphorus (TP) in the BACR were effectively removed under the mixotrophic culture condition. Furthermore, bacterial community profiles and functional genes in the BACR and single acidogenic fermentation reactor were identified. Compared with the single acidogenic fermentation reactor, most of the fermentative bacteria (e.g., Ruminococcus, Christensenellaceae R-7 group, Exiguobacterium, Pseudomonas and Levilinea) were enriched by the BACR. From the genetic perspective, the abundances of dominant genes (ackA, acs and atoD) associated with acetic, propionic and butyric acid production were greatly enhanced in the BACR. In the fatty acid biosynthesis pathway (ko00061), three kinds of high-abundance acetyl-CoA carboxylase genes and eight kinds of downstream functional genes were up-regulated in the BACR. Finally, based on co-occurrence network analysis, the coordination between fermentative bacteria and microalgae in the BACR was revealed. This study provided a deep insight into the advantage and potential of the BACR in mariculture wastewater treatment.