Effect of storage time on the biodegradability of olive oil mill wastewater from the cold extraction of olive oil system

The olive oil processing industry’s liquid effluents (OMW) have a polluting capacity for the ecosystems. This study aimed to evaluate the physicochemical quality of OMW of two varieties of separated and combined olives cultivated in Khenchela Eastern Algeria, from the cold extraction of the olive oil extraction system. These was to determine their degree of pollution and biodegradability during one year of storage at ambient temperature to recommend the correct treatment for each storage time. Results of the measured parameters pH, EC,TSS percent, H2O percent, lipids, DM, OM, MM, VM, COT percent, NTK percent, C/N, BOD5, COD, BI, TOM, BOD5/COD show that wastewater from olive oil mills has an acid pH, and they are very loaded with organic matter evaluated in terms of COD and BOD5, quite filled with minerals. The storage of olive mill waste can reduce progressively the pollution caused by this waste. Whereas during one year, the reduction rate of COD, BOD5, TOM, BI, is respectively 29.4%, 54.8%, 39.16%, 54.2%, but C/N, BOD5/COD continue to increase as well as pH that continues to decrease during the storage. Accordingly, storing olive mill waste during a year reduces its pollution rate, so it is slowly biodegradable. When disposing of it, an adequate treatment procedure must be required to protect the environment.

Phylogenomic and biochemical analysis reassesses temperate marine yeast Yarrowia lipolytica NCIM 3590 to be Yarrowia bubula

Yarrowia clade contains yeast species morphologically, ecologically, physiologically and genetically diverse in nature. Yarrowia lipolytica NCIM 3590 (NCIM 3590), a biotechnologically important strain, isolated from Scottish sea waters was reinvestigated for its phenotypic, biochemical, molecular and genomic properties as it exhibited characteristics unlike Y. lipolytica, namely, absence of extracellular lipolytic activity, growth at lower temperatures (less than 20 °C) and in high salt concentrations (10% NaCl). Molecular identification using ITS and D1/D2 sequences suggested NCIM 3590 to be 100% identical with reference strain Yarrowia bubula CBS 12934 rather than Y. lipolytica CBS 6124 (87% identity) while phylogenetic analysis revealed that it clustered with Y. bubula under a separate clade. Further, whole genome sequencing of NCIM 3590 was performed using Illumina NextSeq technology and the draft reported here. The overall genome relatedness values obtained by dDDH (94.1%), ANIb/ANIm (99.41/99.42%) and OrthoANI (99.47%) indicated proximity between NCIM 3590 and CBS 12934 as compared to the reference strain Y. lipolytica. No extracellular lipase activity could be detected in NCIM 3590 while LIP2 gene TBLASTN analysis suggests a low 42% identity with e value 2 e⁻⁷⁷ and 62% coverage. Hence molecular, phylogenetic, genomics, biochemical and microbial analyses suggests it belongs to Yarrowia bubula.

Bioremediation of palm oil mill effluent (POME) using indigenous Meyerozyma guilliermondii

Despite being a key Malaysian economic contributor, the oil palm industry generates a large quantity of environmental pollutant known as palm oil mill effluent (POME). Therefore, the need to remediate POME has drawn a mounting interest among environmental scientists. This study has pioneered the application of Meyerozyma guilliermondii with accession number (MH 374161) that was isolated indigenously in accessing its potential to degrade POME. This strain was able to treat POME in shake flask experiments under aerobic condition by utilising POME as a sole source of carbon. However, it has also been shown that the addition of suitable carbon and nitrogen sources has significantly improved the degradation potential of M. guilliermondii. The remediation of POME using this strain resulted in a substantial reduction of chemical oxygen demand (COD) of 72%, total nitrogen of 49.2% removal, ammonical nitrogen of 45.1% removal, total organic carbon of 46.6% removal, phosphate of 60.6% removal, and 92.4% removal of oil and grease after 7 days of treatment period. The strain also exhibited an extracellular lipase activity which promotes better wastewater treatment. Additionally, Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) analyses have specifically shown that M. guilliermondii strain can degrade hydrocarbons, fatty acids, and phenolic compounds present in the POME. Ultimately, this study has demonstrated that M. guilliermondii which was isolated indigenously exhibits an excellent degrading ability. Therefore, this strain is suitable to be employed in the remediation of POME, contributing to a safe discharge of the effluent into the environment.

Production of Added-Value Chemical Compounds through Bioconversions of Olive-Mill Wastewaters Blended with Crude Glycerol by a Yarrowia lipolytica Strain

Olive mill wastewaters (OMW) are the major effluent deriving from olive oil production and are considered as one of the most challenging agro-industrial wastes to treat. Crude glycerol is the main by-product of alcoholic beverage and oleochemical production activities including biodiesel production. The tremendous quantities of glycerol produced worldwide represent a serious environmental challenge. The aim of this study was to assess the ability of Yarrowia lipolytica strain ACA-DC 5029 to grow on nitrogen-limited submerged shake-flask cultures, in crude glycerol and OMW blends as well as in media with high initial glycerol concentration and produce biomass, cellular lipids, citric acid and polyols. The rationale of using such blends was the dilution of concentrated glycerol by OMW to (partially or fully) replace process tap water with a wastewater stream. The strain presented satisfactory growth in blends; citric acid production was not affected by OMW addition (Citmax~37.0 g/L, YCit/Glol~0.55 g/g) and microbial oil accumulation raised proportionally to OMW addition (Lmax~2.0 g/L, YL/X~20% w/w). Partial removal of color (~30%) and phenolic compounds (~10% w/w) of the blended media occurred. In media with high glycerol concentration, a shift towards erythritol production was noted (Erymax~66.0 g/L, YEry/Glol~0.39 g/g) simultaneously with high amounts of produced citric acid (Citmax~79.0 g/L, YCit/Glol~0.46 g/g). Fatty acid analysis of microbial lipids demonstrated that OMW addition in blended media and in excess carbon media with high glycerol concentration favored oleic acid production.

Biomass behaviour in a conventional activated sludge system treating olive mill wastewater

The current work aims to study the biomass behaviour in a continuous mode activated sludge system (ASS) treating olive mill wastewater (OMWW) through an increasing OMWW food to microorganism ration (F/M). To this end, the biomass growth, the specific oxygen uptake rate (SOUR), microbial characterization, sludge volume index (SVI) as well as COD and phenolic compounds removal efficiencies were examined over time. Results showed a successful growth of the biomass that reached 6.79 g_TSS l^-1 and 5.42 g_VSS l^-1. Its viability, its adaptability, and its good physiological activity were confirmed by the obtained result of SOUR with an average of 9.95 mg_O2 g_VSS^-1h^-1, as well as aerobic microbial population characterization in terms of aerobic revivable bacteria at 22°C and 37°C, Pseudomonas sp., mould and yeast and total fungi. The concentration of these strains characterized by their ability to degrade effectively COD and phenolic compounds increased significantly (p < .05) over time. This demonstrated a great promptness in response to the increasing OMWW mass ratio. For all treatment steps, removal efficiencies were high and reached 95% of COD and 93% of phenolic compounds, also the flocs settleability shown by SVI measurement was optimal.

Characterization of aerobic oil and grease-degrading bacteria in wastewater

A bacterial consortium that degrades cooking oil (CO) has been isolated in wastewater (WW) samples, by enrichment in olive CO. This consortium could degrade 90% of CO within 7-9 days (from an initial 1% [w/v]), and it is more active at alkaline conditions. The 16S ribonucleic acid (RNA) gene analysis showed that it contains five bacterium species: Stenotrophomonas rhizophila, Sphingobacterium sp., Pseudomonas libanensis, Pseudomonas poae and Pseudomonas aeruginosa. This consortium can degrade the free fatty acids (FFA): palmitic, stearic, oleic, linoleic and linolenic acids; glycerol, glucose and amylose; and albumin, but could not efficiently degrade carboxymethyl-cellulose. Each strain could also degrade CO and FFAs. The level of bacterial crude-activity of extracellular lipases was found to be between 0.2 and 4U/ml. Using synthetic WW, the consortium could reduce 80% of the chemical oxygen demand [from 10550 ± 2828 mg/l], 80% of nitrogen (from 410 ± 78 mgl/l) and 57% of phosphorus (from 93 ± 25 mg/l). Thus, this consortium can be utilized in the removal of CO from WW.

Yarrowia lipolytica and pollutants: Interactions and applications

Yarrowia lipolytica is a dimorphic, non-pathogenic, ascomycetous yeast species with distinctive physiological features and biochemical characteristics that are significant in environment-related matters. Strains naturally present in soils, sea water, sediments and waste waters have inherent abilities to degrade hydrocarbons such as alkanes (short and medium chain) and aromatic compounds (biphenyl and dibenzofuran). With the application of slow release fertilizers, design of immobilization techniques and development of microbial consortia, scale-up studies and in situ applications have been possible. In general, hydrocarbon uptake in this yeast is mediated by attachment to large droplets (via hydrophobic cell surfaces) or is aided by surfactants and emulsifiers. Subsequently, the internalized hydrocarbons are degraded by relevant enzymes innately present in the yeast. Some wild-type or recombinant strains also detoxify nitroaromatic (2,4,6-trinitrotoluene), halogenated (chlorinated and brominated hydrocarbons) and organophosphate (methyl parathion) compounds. The yeast can tolerate some metals and detoxify them via different biomolecules. The biomass (unmodified, in combination with sludge, magnetically-modified and in the biofilm form) has been employed in the biosorption of hexavalent chromium ions from aqueous solutions. Yeast cells have also been applied in protocols related to nanoparticle synthesis. The treatment of oily and solid wastes with this yeast reduces chemical oxygen demand or value-added products (single cell oil, single cell protein, surfactants, organic acids and polyalcohols) are obtained. On account of all these features, the microorganism has established a place for itself and is of considerable value in environment-related applications.

The microbiology of olive mill wastes

Olive mill wastes (OMWs) are high-strength organic effluents, which upon disposal can degrade soil and water quality, negatively affecting aquatic and terrestrial ecosystems. The main purpose of this review paper is to provide an up-to-date knowledge concerning the microbial communities identified over the past 20 years in olive mill wastes using both culture-dependent and independent approaches. A database survey of 16S rRNA gene sequences (585 records in total) obtained from olive mill waste environments revealed the dominance of members of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Actinobacteria. Independent studies confirmed that OMW microbial communities' structure is cultivar dependent. On the other hand, the detection of fecal bacteria and other potential human pathogens in OMWs is of major concern and deserves further examination. Despite the fact that the degradation and detoxification of the olive mill wastes have been mostly investigated through the application of known bacterial and fungal species originated from other environmental sources, the biotechnological potential of indigenous microbiota should be further exploited in respect to olive mill waste bioremediation and inactivation of plant and human pathogens. The implementation of omic and metagenomic approaches will further elucidate disposal issues of olive mill wastes.

Aspergillus niger P6 and Rhodotorula mucilaginosa CH4 used for olive mill wastewater (OMW) biological treatment in single pure and successive cultures

The aim of this study was to investigate the Rhodotorula mucilaginosa CH4 and Aspergillus niger P6 abilities to purify olive mill wastewater (OMW) in single pure and mixed cultures during the treatment. Both fungi were molecularly identified. OMW was used at five dilutions from 5% to 30% with chemical oxygen demand (COD) ranging from 11,600 to 24,600 mg L(-1). Firstly, each fungus was used separately, then they were successively used to treat the OMW. In single pure culture, A. niger showed a better efficiency in OMW purification than R. mucilaginosa. Furthermore, when successively used, the two studied strains exhibited improvements in the decrease of COD, polyphenolic compounds concentration and effluent colour. COD removals were 95.68-56.71% by R. mucilaginosa and 98.02-69.51% by A. niger for OMW dilutions varying from 5% to 30%. Both strains showed an important polyphenolic compounds removal of 83-45% by R. mucilaginosa and 94-58% by A. niger, in accordance with the OMW COD initially used. The COD and phenolic compound removals fitted simple equation models, with high regression coefficients. The strains' growth kinetics decreased according to the OMW concentration, but, when successively used, fungal growth was improved, allowing efficient effluent treatment.

Pretreatment of synthetic dairy wastewater using the sophorolipid-producing yeast Candida bombicola

The presence of high strength fats and oils in dairy industry wastewaters poses serious challenges for biological treatment systems, and, therefore, its pretreatment is necessary in order to remove them. In the present study, synthetic dairy wastewater prepared in the laboratory was pretreated using the sophorolipid-producing yeast Candida bombicola in a laboratory-scale bioreactor under batch, fed-batch, and continuous modes of operation. To support the yeast growth, the wastewater was supplemented with sugarcane molasses (1% w/v) and yeast extract (0.1% w/v). Results from the batch operated fermentor revealed complete utilization of fats present in the wastewater within 96 h with more than 93% COD removal efficiency. The yeast was, however, able to pretreat the wastewater more quickly and efficiently under fed-batch mode of operation than under batch operated condition in the same fermentor. Continuous experiments were carried out with a wastewater retention time of 28 h in the reactor; results showed very good performance of the system in complete utilization of fats and COD removal efficiency of more than 90%. The study proved the excellent potential of the biosurfactant-producing yeast in pretreating high-fat- and oil-containing dairy industry wastewater.

Removal of chromium (VI) ions from aqueous solution by adsorption onto two marine isolates of Yarrowia lipolytica

The removal of chromium (VI) ions from aqueous solutions by the biomass of two marine strains of Yarrowia lipolytica (NCIM 3589 and 3590) was studied with respect to pH, temperature, biomass, sea salt concentration, agitation speed, contact time and initial concentration of chromium (VI) ions. Maximum biosorption was observed at pH 1.0 and at a temperature of 35 degrees C. Increase in biomass and sea salts resulted in a decreased metal uptake. With an agitation speed of 130 rpm, equilibrium was attained within 2h. Under optimum conditions, biosorption was enhanced with increasing concentrations of Cr (VI) ions. NCIM 3589 and 3590 displayed a specific uptake of Cr (VI) ions of 63.73+/-1.3 mg g(-1) at a concentration of 950 ppm and 46.09+/-0.23 mg g(-1) at 955 ppm, respectively. Scatchard plot analysis revealed a straight line allowing the data to be fitted in the Langmuir model. The adsorption data obtained also fitted well to the Freundlich isotherm. The surface sequestration of Cr (VI) by Y. lipolytica was investigated with a scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS) as well as with ED-X-ray fluorescence (ED-XRF). Fourier transform infrared (FTIR) spectroscopy revealed the involvement of carboxyl, hydroxyl and amide groups on the cell surfaces in chromium binding.

Biodegradation of oil wastewater by free and immobilized Yarrowia lipolytica W29

The ability of Yarrowia lipolytica W29 immobilized by calcium alginate to degrade oil and chemical oxygen demand (COD) was examined. The degradation rules of oil and COD by immobilized cells with the cell density of 6.65 x 106 CFU/mL degraded 2000 mg/L oil and 2000 mg/L COD within 50 h at 30 degrees C (pH 7.0, 150 r/min), similarly to those of free cells, and the degradation efficiencies of oil and COD by immobilized cells were above 80%, respectively. The factors affecting oil and COD degradation by immobilized cells were investigated, the results showed that immobilized cells had high thermostability compared to that of free cells, and substrate concentration significantly affected degrading ability of immobilized cells. Storage stability and reusability tests revealed that the oil degradation ability of immobilized cells was stable after storing at 4 degrees C for 30 d and reuse for 12 times, respectively, the COD degradation rate of immobilized cells was also maintained 82% at the sixth cycle. These results suggested that immobilized Y. lipolytica might be applicable to a wastewater treatment system for the removal of oil and COD.

A review on hydrolytic enzymes in the treatment of wastewater with high oil and grease content

Wastewater from dairies and slaughterhouses contains high levels of fats and proteins that present low biodegradability. A large number of pretreatment systems are employed to remove oil and grease (O&G) to prevent a host of problems that may otherwise arise in the biological process, and reduce the efficiency of the treatment station. Problems caused by excessive O&G include a reduction in the cell-aqueous phase transfer rates, a sedimentation hindrance due to the development of filamentous microorganisms, development and flotation of sludge with poor activity, clogging and the emergence of unpleasant odors. Therefore the application of a pretreatment to hydrolyze and dissolve lipids may improve the biological degradation of fatty wastewaters, accelerating the process and improving time efficiency. However thus far, only a few studies describing the degradation of fats and oils by alkaline/acid/enzymatic hydrolysis have been reported; the treatment of effluents from several origins is a new and promising application for lipases. Among the strains that produce the hydrolytic enzymes studied, the fungus Penicillium restrictum is a particularly promising one. When cultivated in low-cost solid medium composed of agro-industrial waste, P. restrictum produces a pool of hydrolases capable of degrading the most complex organic compounds. This degradation enables a considerable increase in organic matter removal efficiency to be realized, which results in the attainment of a high-quality effluent in the subsequent biological treatment stage. Consequently, there is presently a wide variety of ongoing scientific investigation in the field of developing enzymatic hydrolysis processes to precede traditional biological treatment.

Identification and characterisation of LIP7 and LIP8 genes encoding two extracellular triacylglycerol lipases in the yeast Yarrowia lipolytica

In the lipolytic yeast Yarrowia lipolytica, the LIP2 gene was previously reported to encode an extracellular lipase. The growth of a Deltalip2 strain on triglycerides as sole carbon source suggest an alternative pathway for triglycerides utilisation in this yeast. Here, we describe the isolation and the characterisation of the LIP7 and LIP8 genes which were found to encode a 366 and a 371-amino acid precursor protein, respectively. These proteins which belong to the triacylglycerol hydrolase family (EC 3.1.1.3) presented a high homology with the extracellular lipase CdLIP2 and CdLIP3 from Candida deformans. The physiological function of the lipase isoenzymes was investigated by creating single and multi-disrupted strains. Lip7p and Lip8p were found to correspond to active secreted lipases. The lack of lipase production in a Deltalip2 Deltalip7 Deltalip8 strain suggest that no additional extracellular lipase remains to be discovered in Y. lipolytica. The substrate specificity towards synthetic ester molecules indicates that Lip7p presented a maximum activity centred on caproate (C6) while that of Lip8p is in caprate (C10).

2,4,6-trinitrotoluene transformation by a tropical marine yeast, Yarrowia lipolytica NCIM 3589

Yarrowia lipolytica NCIM 3589, a tropical marine degrader of hydrocarbons and triglycerides transformed 2,4,6-trinitrotoluene (TNT) very efficiently. Though this yeast could not utilize TNT as the sole carbon or nitrogen source, it was capable of reducing the nitro groups in TNT to aminodinitrotoluene (ADNT). In a complete medium containing glucose and ammonium sulphate as the available carbon and nitrogen sources respectively, the culture was able to completely transform 1 mM (227 ppm) of TNT under such conditions. A dual pathway was found to be functional, one of which resulted in the formation of the hydride-Meisenheimer complex (H(-)TNT) as a transiently accumulating metabolite that was subsequently denitrated to 2,4-dinitrotoluene (2,4-DNT), whereas the other pathway resulted in the formation of amino derivatives. The presence of increasing amounts of reducing equivalents in the form of glucose promoted better growth and the nitroreductases of this yeast to reduce the aromatic ring to 2,4-DNT although, the reduction of the nitro groups to amino groups was the major functional pathway. The ability of this tropical marine yeast to transform TNT into products such as 2,4-DNT which in turn could be metabolized by other microbes has implications in the use of this yeast for bioremediation of TNT polluted marine environments.

Palm oil mill effluent treatment by a tropical marine yeast

Palm oil mill effluent (POME), from a factory site in India contained about 250,000 mg l(-1) chemical oxygen demand (COD), 11,000 mg l(-1) biochemical oxygen demand, 65 mg l(-1) total dissolved solids and 9000 mg l(-1) of chloroform-soluble material. Treatment of this effluent using Yarrowia lipolytica NCIM 3589, a marine hydrocarbon-degrading yeast isolated from Mumbai, India, gave a COD reduction of about 95% with a retention time of two days. Treatment with a chemical coagulant further reduced the COD and a consortium developed from garden soil clarified the effluent and adjusted the pH to between 6 and 7. The complete treatment reduced the COD content to 1500 mg l(-1) which is a 99% reduction from the original.

Autocloning and amplification of LIP2 in Yarrowia lipolytica

We synthesized a Yarrowia lipolytica strain overproducing lipase for industrial applications by using long terminal repeat (zeta) of the Y. lipolytica retrotransposon Ylt1 and an allele of URA3 with a promoter deletion to construct JMP3. JMP3 is a derivative of plasmid pHSS6 carrying a NotI-NotI cassette which contains a defective URA3 allele, a polylinker sequence, and the zeta region for targeting to multiple sites in the genome of the recipient. We inserted the LIP2 gene (encoding extracellular lipase) under the control of the strong POX2 promoter into JMP3 to generate JMP6. The pHSS6 region was removed by NotI digestion prior to transformation. Two Y. lipolytica strains transformed with the JMP6 LIP2 cassette had a mean of 10 integrated copies devoid of the Escherichia coli region, corresponding to an autocloning event. The copy number in the transformants was stable even after 120 generations in nonselective and lipase-inducing conditions. The resulting strains could produce 0.5 g of active lipase per liter in the supernatant, 40 times more than the single-copy strain with the LIP2 promoter. This work provides a new expression system in Y. lipolytica that results in strains devoid of bacterial DNA and in strains producing a high level of lipase for industrial uses, waste treatment, and pancreatic insufficiency therapy.

Evaluation of acyl coenzyme A oxidase (Aox) isozyme function in the n-alkane-assimilating yeast Yarrowia lipolytica

We have identified five acyl coenzyme A (CoA) oxidase isozymes (Aox1 through Aox5) in the n-alkane-assimilating yeast Yarrowia lipolytica, encoded by the POX1 through POX5 genes. The physiological function of these oxidases has been investigated by gene disruption. Single, double, triple, and quadruple disruptants were constructed. Global Aox activity was determined as a function of time after induction and of substrate chain length. Single null mutations did not affect growth but affected the chain length preference of acyl-CoA oxidase activity, as evidenced by a chain length specificity for Aox2 and Aox3. Aox2 was shown to be a long-chain acyl-CoA oxidase and Aox3 was found to be active against short-chain fatty acids, whereas Aox5 was active against molecules of all chain lengths. Mutations in Aox4 and Aox5 resulted in an increase in total Aox activity. The growth of mutant strains was analyzed. In the presence of POX1 only, strains did not grow on fatty acids, whereas POX4 alone elicited partial growth, and the growth of the double POX2-POX3-deleted mutant was normal excepted on plates containing oleic acid as the carbon source. The amounts of Aox protein detected by Western blotting paralleled the Aox activity levels, demonstrating the regulation of Aox in cells according to the POX genotype.