Outdoor microalgae cultivation in airlift photobioreactor at high irradiance and temperature conditions: effect of batch and fed-batch strategies, photoinhibition, and temperature stress.

The microalgae Scenedesmus abundans cultivated in five identical airlift photobioreactors (PBRs) in batch and fed-batch modes at the outdoor tropical condition. The microalgae strain S. abundans was found to tolerate high temperature (35-45 °C) and high light intensity (770-1690 µmol m- 2 s- 1). The highest biomass productivities were 152.5-162.5 mg L- 1 day- 1 for fed-batch strategy. The biomass productivity was drastically reduced due to photoinhibition effect at a culture temperature of > 45 °C. The lipid compositions showed fatty acids mainly in the form of saturated and monounsaturated fatty acids (> 80%) in all PBRs with Cetane number more than 51. The fed-batch strategies efficiently produced higher biomass and lipid productivities at harsh outdoor conditions. Furthermore, the microalgae also accumulated omega-3 fatty acid (C18:3) up to 14% (w/w) of total fatty acid at given outdoor condition.

New approaches for itaconic acid production: bottlenecks and possible remedies.

Currently, growing attention is being devoted to the conversion of biomass into value-added products, such as itaconic acid (IA), which is considered as the cleanest alternative to petroleum-based acrylic acid. IA is an unsaturated dicarboxylic acid that is used as a building block chemical for the production of several value-added products such as poly-itaconic acid. IA and its derivatives have a wide range of potential applications in textile, paint, pharmaceutical and chemical industries. Presently, industries are producing IA on the large scale by fermentation from glucose. However, due to the primary utility of glucose as a food, it cannot meet the global demand for IA production in an economical way. The main challenge, so far, has been the production technology, which does not support cost-effective and competitive production of IA. This review discusses the various bottlenecks faced during each step of IA production, along with possible remedies to deal with these problems. Furthermore, it reviews the recent progress in fermentative IA production and sheds light on different microorganisms used, potential substrates and fermentation conditions. The review also covers market potential for IA, which indicates that IA can be produced cost-effectively from sustainable substrates, and it has the potential to replace petrochemicals in the near future.

Recent advancements in the mitigation of obnoxious nitrogenous gases.

Nitrogenous gaseous emissions commonly have an obnoxious odor associated with it, which when discharged into the environment results in serious environmental problems and health hazards. Several strategies for mitigation of nitrogenous odorants have been reported which include physical, chemical and biological methods. Biological treatments are widely employed because of their efficiency even at low concentration, where physical and chemical methods are not effective. Most commonly used biological treatment methods are biofiltration, biotrickling filters and membrane bioreactors with innovative reactor design, mixing pattern, and air sparging, for example FEBR, ALR, etc. These treatment methods require a critical assessment for the mitigation of obnoxious nitrogen emissions, especially in the context of environmental protection. This review offers a critical evaluation of treatment methods for the mitigation of nitrogenous odorous compound with a key emphasis on biological treatment systems. Also, various mathematical modelling techniques required for optimized operation of biotreatment systems has been discussed.

Transformation Products of Carbamazepine (CBZ) After Ozonation and their Toxicity Evaluation Using Pseudomonas sp. Strain KSH-1 in Aqueous Matrices.

Carbamazepine (CBZ) is an anti-epileptic and anti-convulsant drug widely used for the treatment of epilepsy and other bipolar disorders. Ozone as an advanced oxidation process has been widely used for the degradation of CBZ resulting in the formation of transformation products (ozonides). The present research aims to isolate and identify potential microorganism, capable of degradation of CBZ and its transformation products. The cell viability and cytotoxicity of pure CBZ and their ozone transformation products were evaluated using the cells of Pseudomonas sp. strain KSH-1 through cell viability assay tests. The cells metabolic activity was assessed at varying CBZ concentrations (~ 10-25 ppm, pure CBZ) and cumulatively for ozone transformation products. For pure CBZ, % cell viability decreases as CBZ concentration increases, while, in case of post-ozonated CBZ transformation products, the viability decreases initially and then increases upon exposure of ozone with a maximum cell viability of 97 ± 2.8% evaluated for 2 h post-ozonated samples.

Microbial population shift caused by sulfamethoxazole in engineered-Soil Aquifer Treatment (e-SAT) system.

The engineered-Soil Aquifer Treatment (e-SAT) system was exploited for the biological degradation of Sulfamethoxazole (SMX) which is known to bio-accumulate in the environment. The fate of SMX in soil column was studied through laboratory simulation for a period of 90 days. About 20 ppm SMX concentration could be removed in four consecutive cycles in e-SAT. To understand the microbial community change and biological degradation of SMX in e-SAT system, metagenomic analysis was performed for the soil samples before (A-EBD) and after SMX exposure (B-EBD) in the e-SAT. Four bacterial phyla were found to be present in both the samples, with sample B-EBD showing increased abundance for Actinobacteria, Bacteroidetes, Firmicutes and decreased Proteobacterial abundance compared to A-EBD. The unclassified bacteria were found to be abundant in B-EBD compared to A-EBD. At class level, classes such as Bacilli, Negativicutes, Deltaproteobacteria, and Bacteroidia emerged in sample B-EBD owing to SMX treatment, while Burkholderiales and Nitrosomonadales appeared to be dominant at order level after SMX treatment. Furthermore, in response to SMX treatment, the family Nitrosomonadaceae appeared to be dominant. Pseudomonas was the most dominating bacterial genus in A-EBD whereas Cupriavidus dominated in sample B-EBD. Additionally, the sulfur oxidizing bacteria were enriched in the B-EBD sample, signifying efficient electron transfer and hence organic molecule degradation in the e-SAT system. Results of this study offer new insights into understanding of microbial community shift during the biodegradation of SMX.

Itaconic Acid Production by Filamentous Fungi in Starch-Rich Industrial Residues.

Several fungi and starch-rich industrial residues were screened for itaconic acid (IA) production. Out of 15 strains, only three fungal strains were found to produce IA, which was confirmed by HPLC and GC-MS analysis. These strains were identified as Aspergillus terreus strains C1 and C2, and Ustilago maydis strain C3 by sequencing of 18S rRNA gene and internal transcribed spacer regions. Cis-aconitate decarboxylase (cad) gene, which encodes a key enzyme in IA production in A. terreus, was characterized from strains C1 and C2. C1 and C2 cad gene sequences showed about 96% similarity to the only available GenBank sequence of A. terreus cad gene. 3-D structure and cis-aconitic acid binding pocket of Cad enzyme were predicted by structural modeling. Rice, corn and potato starch wastes were screened for IA production. These materials were enzymatically hydrolyzed under experimentally optimized conditions resulting in the highest glucose production of 230 mg/mL from 20% potato waste. On comparing the production potential of selected strains with different wastes, the best IA production was achieved with strain C1 (255.7 mg/L) using potato waste. Elemental composition as well as batch-to-batch variation in waste substrates were analyzed. The difference in IA production from two different batches of potato waste was found to inversely correlate with their phosphorus content, which indicated that A. terreus produced IA under phosphate limiting condition. The potato waste hydrolysate was deionized to remove inhibitory ions like phosphate, resulting in improved IA production of 4.1 g/L by C1 strain, which is commercially competitive.

Treatment of ferrous-NTA-based NO x scrubber solution by an up-flow anaerobic packed bed bioreactor.

A bench scale system consisting of an up-flow packed bed bioreactor (UAPBR) made of polyurethane foam was used for the treatment and regeneration of aqueous solution of ferrous-NTA scrubbed with nitric oxide (NO). The biomass in the UAPBR was sequentially acclimatized under denitrifying and iron reducing conditions using ethanol as electron donor, after which nitric oxide (NO) gas was loaded continuously to the system by absorption. The system was investigated for different parameters viz. pH, removal efficiency of nitric oxide, biological reduction efficiency of Fe(II)NTA-NO and COD utilization. The Fe(II)NTA-NO reduction efficiency reached 87.8 % at a loading rate of 0.24 mmol L(-1) h(-1), while the scrubber efficiency reached more than 75 % with 250 ppm NO. Stover-Kincannon and a Plug-flow kinetic model based on Michaelis-Menten equation were used to describe the UAPBR performance with respect to Fe(II)NTA-NO and COD removal. The Stover-Kincannon model was found capable of describing the Fe(II)NTA-NO reduction (R m = 8.92 mM h(-1) and K NO = 11.46 mM h(-1)) while plug-flow model provided better fit to the COD utilization (U m = 66.62 mg L(-1) h(-1), K COD = 7.28 mg L(-1)). Analyses for pH, Fe(III)NTA, ammonium, nitrite concentration, and FTIR analysis of the medium samples indicated degradation of NTA, which leads to ammonium and nitrite accumulation in the medium, and affect the regeneration process.

Treatment of waste gas containing low concentration of dimethyl sulphide in a high performance biotrickling filter.

A bench-scale biotrickling filter was operated in the laboratory for the treatment of dimethyl sulphide (DMS). The biotrickling filter was packed with pre-sterilized polyurethane foam and seeded with biomass developed from garden soil enriched with DMS. The biotrickling filter was operated for the generation of process parameters. The biotrickling filter could remove an average removal efficiency of 40.95% at an effective bed contact time of 84 sec with an average loading rate of 0.56 mg/m3/h. Evaluation of microbiological status of the biotrickling filter indicated the presence of other bacterial cultures viz. Paenibacillus polymyxa, and Bacillus megaterium, besides Bacillus sphaericus.

Air-lift reactor system for the treatment of waste-gas-containing monochlorobenzene.

An air-lift bioreactor (ALR) system, applied for the treatment of waste-gas-containing monochlorobenzene (MCB) was seeded with pure culture of Acinetobacter calcoaceticus, isolated from soil as a starter seed. It was found that MCB was biologically converted to chloride as chloride was mineralized in the ALR. After the built up of the biomass in the ALR, the reactor parameters which have major influence on the removal efficiency and elimination capacity were studied using response surface methodology. The data generated by running the reactor for 150 days at varying conditions were fed to the model with a target to obtain the removal efficiency above 95% and the elimination capacity greater than 60%. The data analysis indicated that inlet loading was the major parameter affecting the elimination capacity and removal efficiency of >95%. The reactor when operated at optimized conditions resulted in enhanced performance of the reactor.

Treatment of mixtures of toluene and n-propanol vapours in a compost-woodchip-based biofilter.

The present work describes the biofiltration of mixture of n-propanol (as a model hydrophilic volatile organic compound (VOC)) and toluene (as a model hydrophobic VOC) in a biofilter packed with a compost-woodchip mixture. Initially, the biofilter was fed with toluene vapours at loadings up to 175 g m(-3) h(-1) and removal efficiencies of 70%-99% were observed. The biofilter performance when removing mixtures of toluene and n-propanol reached elimination capacities of up to 67g(toluene) m(-3) h(-1) and 85 g(n-propanol) m(-3) h(-1) with removal efficiencies of 70%-100% for toluene and essentially 100% for n-propanol. The presence of high n-propanol loading negatively affected the toluene removal; however, n-propanol removal was not affected by the presence of toluene and was effectively removed in the biofilter despite high toluene loadings. A model for toluene and n-propanol biofiltration could predict the cross-inhibition effect of n-propanol on toluene removal.

Microbial degradation of pyridine and alpha-picoline using a strain of the genera Pseudomonas and Nocardia sp.

Biodegradation of pyridine and alpha-picoline (2-methyl pyridine) by Pseudomonas pseudoalcaligenes-KPN and Nocardia sp. isolated from garden soil were investigated in batch culture experiments. Pyridine and alpha-picoline (50-200 mg L(-1)) were used as sole source of carbon and energy in the investigation. The kinetic constants were evaluated for pyridine and alpha-picoline degradation under optimized nutritional (C, N, P) and environmental (pH, temperature) conditions. The values of bio-kinetic constant obtained in the present investigation indicate the usefulness of both the cultures for treatment of waste containing pyridine and its derivatives.

Optimization and scale up of itaconic acid production from potato starch waste in stirred tank bioreactor.

Present study used Aspergillus terreus strain C1 isolated from mangrove soil for itaconic acid (IA) production from potato starch waste. Fermentation parameters were optimized by classical one factor approach and statistical experimental designs, such as Plackett-Burman and response surface designs. Anionic deionization of potato waste was found to be a very effective, economic, and easy way of improving IA production. The increase in IA production by deionization was found to correlate with removal of phosphate. In our knowledge, this is the first report on application of deionization of potato waste to enhance IA production. Other parameters like inoculum development conditions, pH, presence of peptone and certain salts in the medium also significantly affected IA production. IA production by strain C1 increased 143-fold during optimization when compared with the starting condition. The optimized IA level (35.75 g/L) was very close to the maximum production predicted by RSM (38.88 g/L). Bench scale production of IA was further optimized in 3-L stirred tank reactor by varying parameters like agitation and aeration rate. The maximum IA production of 29.69 g/L was obtained under the agitation speed of 200 rpm and aeration rate of 0.25 vvm. To the best of our knowledge, it is the first report on IA production from potato starch waste at bioreactor level. © 2019 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2774, 2019.

Current practices and challenges in using microalgae for treatment of nutrient rich wastewater from agro-based industries.

Considerable research activities are underway involving microalgae species in order to treat industrial wastewater to address the waste-to-bioenergy economy. Several studies of wastewater treatment using microalgae have been primarily focused on removal of key nutrients such as nitrogen and phosphorus. Although the use of wastewater would provide nutrients and water for microalgae growth, the whole process is even more complex than the conventional microalgae cultivation on freshwater media. The former one adds several gridlocks to the system. These gridlocks are surplus organic and inorganic nutrients concentration, pH of wastewater, wastewater color, total dissolved solids (TDS), microbial contaminants, the scale of photobioreactor, batch versus continuous system, harvesting of microalgae biomass etc. The present review discusses, analyses, and summarizes key aspects involved in the treatment of wastewaters from distillery, food/snacks product processing, and dairy processing industry using microalgae along with sustainable production of its biomass. This review further evaluates the bottlenecks for individual steps involved in the process such as pretreatment of wastewater for contaminants removal, concentration tolerance/dilutions, harvesting of microalgae biomass, and outdoor scale-up. The review also describes various strategies to optimize algal biomass and lipid productivities for various wastewater and photobioreactor type. Moreover, the review emphasizes the potential of co-cultivation of microorganism such as yeast and bacteria along with microalgae in the treatment of industrial wastewater.

Integrated bio-oxidation and adsorptive filtration reactor for removal of arsenic from wastewater.

Recently, removal of arsenic from different industrial effluent discharged using simple, efficient and low-cost technique has been widely considered. In this study, removal of arsenic (As) from real wastewater has been studied employing modified bio-oxidation followed by adsorptive filtration method in a novel continuous flow through the reactor. This method includes biological oxidation of ferrous to ferric ions by immobilized Acidothiobacillus ferrooxidans bacteria on granulated activated carbon (GAC) in fixed bed bio-column reactor with the adsorptive filtration unit. Removal efficiency was optimized regarding the initial flow rate of media and ferrous ions concentration. Synthetic wastewater sample having different heavy metal ions such as Arsenic (As), Cobalt (Co), Chromium (Cr), Copper (Cu), Iron (Fe), Lead (Pb) and Manganese (Mn) were also used in the study. The structural and surface changes occurring after the treatment process were scrutinized using FT-IR and Scanning Electron Microscopy (SEM) analysis. The finding showed that not only arsenic can be removed considerably in the bioreactor system, but also removing efficiency was much more (<90%) for other heavy metals in real wastewater sample. The results from TCPL test confirms that solid spent media was non-hazardous and can be safely disposed of. This study verified that combination of bio-oxidation with adsorptive filtration method improves the removal efficiency of arsenic and other heavy metal ions in wastewater sample.

Heterocyclic nitrogenous pollutants in the environment and their treatment options--an overview.

Heterocyclic nitrogenous bases are one of the most important class of compounds containing N as a heteroatom, like pyridine and its derivatives. These compounds are of immense concern from point view of environment since they are known for their toxic and carcinogenic properties, lethal effect on natural biogenic environment and severe odour potential. There is a need to control these compounds from getting discharged into the environment. This paper addresses the different natural/anthropogenic sources which generate these pollutants, their toxicity profile, different physico-chemical treatment methods and especially focuses on biological methods of treatment and combination of these for the efficient removal to achieve a treated effluent quality fit for disposal without causing any damage to the environment.

Pyridine biodegradation in a novel rotating rope bioreactor.

A novel immobilised bioreactor has been developed especially for the treatment of pollutants characterized by high volatility along with high water solubility and low microbial yields. The new bioreactor referred to as the rotating rope bioreactor (RRB) provides higher interfacial area (per unit reactor liquid volume) along with high oxygen mass transfer rate, greater microbial culture stability; and consequently higher substrate loadings and removal rates in comparison to other conventional rectors for the treatment of volatile compounds. Pyridine was used as a model compound to demonstrate the enhanced performance with RRB, when compared to that reported with other conventional bioreactors. The experimental results indicate that the novel RRB system is able to degrade pyridine with removal efficiency of more than 85% at higher pyridine concentration (up to 1000 mg/l) and loading [up to 400 mg/m(2)/h (66.86 g/m(3)/h)], with a shorter hydraulic retention time (9-18 h). The reactor has been in operation for the past 15 months and no loss of activity has been observed.

Biotreatment of waste gas containing pyridine in a biofilter.

Industrial waste gas emissions containing pyridine are generated from pyridine manufacturing industries, and in industrial operations where pyridine is used as a solvent, as an intermediate for synthesis and as a catalyst for a variety of applications. Pyridine has unpleasant fishy odor with an odor index of 2390 and waste gaseous emissions containing pyridine require proper treatment prior to discharge. A biofilter, packed with compost and wood chips and inoculated with Pseudomonas pseudoalcaligenes-KPN for enrichment of pyridine-degrading microorganisms, was operated on a continuous feed basis for a period of more than 2 years. The results indicate that the biofilter medium with optimal moisture content of 68% and an effective bed retention time (EBRT) of 28.50s could degrade pyridine effectively (>99%) at a loading of 434 g pyridine m(-3)h(-1). The treated waste gas was also found to be free from pyridine odor.

Oxidative Stress and Genotoxicity of Zinc Oxide Nanoparticles to Pseudomonas Species, Human Promyelocytic Leukemic (HL-60), and Blood Cells.

In the present study, toxicity of commercial zinc oxide nanoparticles (ZnO NPs) was studied on the bacterium Pseudomonas sp., human promyelocytic leukemia (HL-60) cells, and peripheral blood mononuclear cells (PBMC). The toxicity was assessed by measuring growth, cell viability, and protein expression in bacterial cell. The bacterial growth and viability decreased with increasing concentrations of ZnO NP. Three major proteins, ribosomal protein L1 and L9 along with alkyl hydroperoxides reductase, were upregulated by 1.5-, 1.7-, and 2.0-fold, respectively, after ZnO NP exposure. The results indicated oxidative stress as the leading cause of toxic effect in bacteria. In HL-60 cells, cytotoxic and genotoxic effects along with antioxidant enzyme activity and reactive oxygen species (ROS) generation were studied upon ZnO NP treatment. ZnO NP exhibited dose-dependent increase in cell death after 24-h exposure. The DNA-damaging potential of ZnO NP in HL-60 cells was maximum at 0.05 mg/L concentration. Comet assay showed 70-80% increase in tail DNA at 0.025 to 0.05 mg/L ZnO NP concentration. A significant increase of 1.6-, 1.4-, and 2.0-fold in ROS level was observed after 12 h. Genotoxic potential of ZnO NPs was also demonstrated in PBMC through DNA fragmentation. Thus, ZnO NP, besides being an essential element having antibacterial activity, also showed toxicity towards human cells (HL-60 and PBMC).

Evaluation of biogas production potential of kitchen waste in the presence of spices.

Anaerobic digestion (AD) of kitchen waste (KW) for biogas production is a major challenge to all over the world due to significant compositional variations in KW, such as different types and quantities of spices used for preparing food. Spices may affect the AD process owing to their antimicrobial activity. In this paper, the effect of spices (garlic, red chili, cinnamon, coriander, clove, turmeric, cardamom, black pepper) on AD of KW has been investigated. Batch experiments were carried out to determine the maximum biogas production potential, methane production rate and lag phase for biogas production. Analysis of the results revealed different magnitude of inhibition of the AD process of KW in the presence of different spices. Cinnamon, cardamom and clove resulted >85%, black pepper resulted 75%, while coriander, chili, turmeric and garlic resulted 55-70% reduction in cumulative biogas yield. Elemental analysis showed high concentration of heavy metals in the spices, which along with other bioactive components of the spices could be responsible for the inhibitory effect of the spices on biomethanation. Microbial examination of the digestate also showed a decrease in population of fermentative and methanogenic bacteria in the presence of spices.

Biodegradation of pyridine in a completely mixed activated sludge process.

A potential bacterial culture (P1), isolated from garden soil and identified as Pseudomonas pseudoalcaligenes-KPN, was used as a starter seed to develop the biomass in a completely mixed activated sludge (CMAS) reactor and the system was evaluated for treatment of wastewater containing pyridine. The results of this study indicate that pyridine could be degraded efficiently at a loading of 0.251 kg pyridine kg MLSS(-1) d(-1) (0.156 kg TOC kg MLSS(-1) d(-1)) and at an optimal hydraulic retention time (HRT) of 24 h. Pyridine was used as the sole source of carbon and nitrogen by the biomass. Ammonia-nitrogen (NH3-N) was formed due to the metabolism of the pyridine ring. In the present investigation, the performance of CMAS with reference to pyridine biodegradation and the bio-kinetic constants for the biodegradation of pyridine, in a continuous system, were computed. The results indicate that a CMAS system inoculated with P. pseudoalcaligenes-KPN, under optimum conditions of HRT and pyridine loading, gives a yield coefficient of (Y) 0.29, decay coefficient (Kd) 0.0011 d(-1), maximum growth rate constant (mumax) 0.108 d(-1) and saturation rate constant (Ks) 5.37 mg L(-1) for pyridine.