Conversions of olive mill wastewater‐based media by Saccharomyces cerevisiae through sterile and non‐sterile bioprocesses

BACKGROUND: Olive mill wastewaters (OMWs) are an important residue and several methods have been proposed for their treatment. RESULTS: Remarkable decolorization (~63%) and phenol removal (~34% w/w) from OMW was achieved. In glucose‐based flask sterile cultures, enrichment with OMWs increased ethanol and biomass production compared with cultures without OMWs added. Flask sterile and un‐sterilized cultures demonstrated similar kinetic results. Batch‐bioreactor trials performed showed higher ethanol and lower biomass quantities compared with the respective shake‐flask experiments, while cultures used under un‐sterilized conditions revealed equivalent results to the sterile ones. In non‐sterile bioreactor cultures, OMWs addition enhanced biomass production in comparison with culture with no OMWs added, whereas ethanol biosynthesis was not affected. The maximum ethanol quantity achieved was 52 g L^?1 (conversion yield per sugar consumed of 0.46 g g^?1) in a batch bioreactor non‐sterilized trial with OMW–glucose enriched medium used as substrate, that presented initial reducing sugars concentration at ~115 g L^?1. Fatty acid analysis of cellular lipids demonstrated that in OMW‐based media, cellular lipids containing increased concentrations of oleic and linoleic acid were produced in comparison with cultures with no OMWs added. CONCLUSIONS: S. cerevisiae simultaneously produced bio‐ethanol and biomass and detoxified OMWs, under non‐sterile conditions. © 2012 Society of Chemical Industry     

The use of olive mill wastewater by wild type Yarrowia lipolytica strains: medium supplementation and surfactant presence effect

BACKGROUND: The aim of this work was to study the ability of two different wild type strains of the yeast Yarrowia lipolytica to grow on olive mill wastewater (OMW) and their potential to produce high‐value products such as lipases. Factors that affect cellular growth and OMW degradation were studied, such as nitrogen supplementation, cells concentration and surfactant addition. RESULTS: Both strains, W29 and IMUFRJ 50682, were able to grow in OMW with 19 g L^?1 of COD and approximately 800 mg L^?1 of total phenols concentration. The strain W29 presented the highest potential for extracellular lipase production in OMW medium. Lipase productivity was improved by the medium supplementation with ammonium sulphate up to 6 g L^?1, leading to 80% of COD degradation and 70% of total phenols reduction. The surfactant Tween 80 enhanced cell growth and COD degradation, but had a negative effect on lipase activity. CONCLUSIONS Y. lipolytica has a great potential for OMW valorisation by its use as culture medium for biomass and enzymes production. The operating conditions that favoured lipase production differ from the conditions that improve COD reduction. Copyright © 2008 Society of Chemical Industry     

Biosynthesis of lipids and organic acids by Yarrowia lipolytica strains cultivated on glucose

The biochemical behavior of wild‐type or genetically modified (presenting decreased expression of intracellular acyl‐CoA oxidases) Yarrowia lipolytica strains cultivated on commercial glucose was studied. Flask nitrogen‐limited cultures were performed favoring the production of organic acids (and potentially the accumulation of lipid). Nitrogen depletion induced secretion of citric acid, while intracellular lipid was not produced in high quantities. Maximum total citric acid up to 49 g/L (yield 0.85 g/g glucose) was produced. In some of the wild‐type strains, an increase of glucose in the medium also induced noticeable production of acetic acid. Increasing the amount of added glucose led to an increase in the total lipid quantity (%) produced, although in the stationary growth phase the concentration of lipid declined, indicating lipid degradation even for the genetically modified strains. Total lipid amount did not exceed the value of 14%, while neutral fractions increased with increase in glucose concentration. In all cases, the total microbial lipids and major lipid fractions were composed of C₁₆ and C₁₈ (principally unsaturated) fatty acids. Finally, in several of the strains cultured in media containing a low glucose concentration, unicellular morphology was observed, while at high glucose concentrations mycelia were predominant.     

Fed‐batch fermentation of olive mill wastewaters for lipase production

In the Mediterranean basin countries, huge amounts of olive mill wastewaters (OMW) are produced by the olive oil industry. It constitutes a serious environmental problem, nevertheless its composition turns OMW into a potential growth medium to lipolytic microorganisms. The aim of this work was to study lipase production as well as OMW degradation in fed‐batch cultures of Candida cylindracea CBS 7869, Candida rugosa CBS 2275 and Yarrowia lipolytica W29 (ATCC 20460). Besides the improvement of lipase production, the fed‐batch approach enhanced the effluent degradation, since it led to good COD and lipids reduction, both higher than 50%. C. rugosa achieved the highest value of lipase productivity (130 U L^?1 h^?1), in parallel with highest lipids reduction (77%). This study demonstrates that OMW are becoming a competitive and valuable growth medium in fermentation processes with lipolytic microorganisms. The fed‐batch strategy used proved to be an efficient approach to enhance lipase production from OMW and to reduce significantly the final organic load of the medium. Copyright © 2012 Society of Chemical Industry     

High level of laccases production by Trametes trogii culture on olive mill wastewater‐based media,application in textile dye decolorization

BACKGROUND: Laccases are receiving increasing attention as potential industrial enzymes in various applications. Therefore, it is important to find inexpensive and optimized media for large‐scale commercial production. The present work aims to valorize olive mill wastewater (OMW) by its use as base media for laccases production by Trametes trogii and use of the laccases produced for decolorizing textile dyes. RESULTS: A high yield of 25 120 U L^?1 of laccases was obtained at an OMW:water ratio of 80:20 enriched with 2 g L^?1 of urea corresponding to initial biochemical oxygen demand (BOD₅), chemical oxygen demand (COD) and total phenol concentrations of 18.4, 46 and 4.6 g L^?1 respectively. The partially purified laccases resulted in 85% decolorization of blue tubantin GLL 300 and black tubantin VSF 600, and 45% decolorization of blue solophenyl after 6 h of incubation. Subsequent additions of the same dye dose to the reaction mixture resulted in a very significant decrease in laccases activity after the third dye addition. CONCLUSION: The use of OMW for laccases production is a cost effective process. The laccases produced can be applied to the decolorization of textile wastewaters. Copyright © 2009 Society of Chemical Industry     

Modelling aspects of the biotechnological valorization of raw glycerol: production of citric acid by Yarrowia lipolytica and 1,3‐propanediol by Clostridium butyricum

Raw glycerol, produced in significant quantities during several industrial processes, could be further considered as a potential substrate for microbial conversions. In the present report, modelling approaches are used in order to quantify the kinetic behavior of microorganisms capable of producing growth‐ and non growth‐associated metabolites when cultivated on raw glycerol. Citric acid production by Yarrowia lipolytica strain ACA‐DC 50109 was successfully simulated by Monod‐, Verhlust‐ and Williams‐type models, while the optimized parameter values were found to be similar to those experimentally measured. It has been demonstrated that the production of citric acid from raw glycerol, in terms of specific production rate and conversion yield, was similar or even better as compared with that obtained during cultivation of yeasts or molds on various conventional (eg sugar‐based) media. The production of 1,3‐propanediol by Clostridium butyricum strain F2b from raw glycerol was successfully simulated by a Contois‐type model. It was found that the maximum theoretical 1,3‐propanediol productivity was comparable with the highest one achieved during growth of various bacterial strains on pure glycerol in batch and continuous cultures. Raw glycerol could be used as an alternative substrate for citric acid and 1,3‐propanediol production, and possibly for other microbial products. Copyright © 2003 Society of Chemical Industry     

Effect of lipids and surfactants on extracellular lipase production by Yarrowia lipolytica

The production of extracellular lipase in submerged cultures of Yarrowia lipolytica CECT 1240 has been investigated. Several compounds have been added to the culture medium, in order to assess their efficiency as inducers of lipase production. First, the effect of triglycerides (olive oil, sunflower oil, tributyrin) and fatty acids (oleic acid) has been studied. The highest activity level was obtained with sunflower oil (58 U cm^?3), followed by olive oil (49 U cm^?3). The cultures with tributyrin and oleic acid attained similar activities (33 U cm^?3). Then, several surfactants (Tween 80, Triton X‐100, gum arabic, polyethylene glycol 200) were added to the cultures with sunflower oil, in an attempt to increase the levels of extracellular lipase activity. The obtained activities were slightly lower than those achieved without surfactants. The assay of a wide range of surfactant concentrations in the case of PEG‐200 (with which the highest activity levels had been attained) did not improve the results. This strain secreted lipase concentrations two‐fold higher and showed significantly different behaviour towards the presence of surfactants in the culture medium, compared with other wild‐type Yarrowia lipolytica strains. Copyright © 2003 Society of Chemical Industry     

In‐line mixing for production of citric acid by Candida lipolytica grown on n‐paraffins

This study reports on the effects of internal fermenter and external in‐line agitation and fed‐batch mode of operation on citric acid production from Candida lipolytica using n‐paraffin as the carbon source. An optimum range of fermenter agitation speeds in the range 800–1000 rpm corresponding to Reynolds numbers of 50433–62947 (based on initial batch conditions) seemed to give the best balance between substrate utilization for biomass growth and citric acid production. Proof of concept evidence is presented that indicates that an external in‐line agitator could be used in place of high speed internal agitation to increase citric acid production. However, more work is required to optimize the external agitator concept. Application of multiple fed‐batch feedings can be used to extend the batch fermentation and increase final citric acid concentrations and product yield. Experiments were conducted implementing a three‐cycle fed‐batch process which increased overall citric acid yields to 0.8–1.0 g citric acid g^?1 n‐paraffin, approximately 200% improvement from those found in the normal batch process. The three‐cycle fed‐batch mode of operation also increased the final citric acid concentration to 42 g dm^?3 from about 6 g dm^?3 for normal batch operation. Increased citric acid concentrations in three‐cycle fed‐batch mode was achieved at longer fermentation times. Copyright © 2004 Society of Chemical Industry     

Management scenarios for olive oil mill waste based on characterization and leaching tests

BACKGROUND: Olive oil mill waste is a serious environmental problem in the Mediterranean basin given its particular characteristics of high organic content, seasonal and localized generation, and the type of processing involved. RESULTS: Olive mill waste from a three‐phase mill was characterized by means of total analysis, availability and mobility of the pollutants in order to help the decision‐maker about possible options for its valorization and/or disposal. Water content, loss of ignition, total organic carbon, phenol index and metals concentrations were measured to fully characterize the waste. Three leaching tests (NEN 7341, EN 12457 and UNE CEN‐TS 15364 EX) were carried out to evaluate the environmental hazard of the waste material and the leachates were characterized with respect to electric conductivity, pH, heavy metals, anions and organic pollutants (phenol index and total organic carbon) according to European waste directives. The results were compared with EU regulations for inert, non‐hazardous and hazardous waste disposal. CONCLUSION: It was found that not only organic parameters must be taken into account concerning the fate of this waste material, but also the mobility of heavy metals and anions should be studied. Furthermore, stabilization/solidification processes are recommended before landfill disposal of this kind of agro‐waste material. Copyright © 2011 Society of Chemical Industry     

Treatment of olive mill wastewaters by ozonation,aerobic degradation and the combination of both treatments

The degradation of the pollutant organic matter present in olive oil mill wastewaters (OMW) is carried out by a single ozonation, a single aerobic degradation, and the combination of two successives steps: an ozonation followed by an aerobic degradation, and an aerobic degradation followed by an ozonation. In both single processes, the removal of this contaminant load is followed by means of global parameters which are directly related to the concentration of organic compounds in those effluents: chemical oxygen demand and total aromatic and phenolic contents. In the ozonation, an approximate kinetic study is performed which leads to the evaluation of the apparent kinetic constants for the aromatic reduction, k_A. In the aerobic degradation, the kinetic study is conducted by using the Grau model, which is applied to the experimental data, and leads to the determination of the kinetic parameters of this model, K₂ and n. In the combined processes, a higher COD global reduction is obtained by the successive stages, and an improvement in the removal of the organic material during the second treatment of both processes due to the pretreatment conducted is also observed. This enhancement is shown by an increase of the kinetic parameters (K₂ and n in the aerobic degradation of the pre‐ozonated wastewaters; the apparent constant k_A in the ozonation of the wastewaters preliminary fermented aerobically), in relation to the values obtained for them in the single processes carried out at the same operating conditions. © 1999 Society of Chemical Industry     

Effects of Different Oil Sources and Residues on Biomass and Metabolite Production by Yarrowia lipolytica YB 423-12

Yarrowia lipolytica is known to have the ability to assimilate hydrophobic substrates like triglycerides, fats, and oils, and to produce single-cell oils, lipases, and organic acids. The aim of the present study was to investigate the effects of different oil sources (borage, canola, sesame, Echium, and trout oils) and oil industry residues (olive pomace oil, hazelnut oil press cake, and sunflower seed oil cake) on the growth, lipid accumulation, and lipase and citric acid production by Y. lipolytica YB 423-12. The maximum biomass and lipid accumulation were observed with linseed oil. Among the tested oil sources and oil industry residues, hazelnut oil press cake was the best medium for lipase production. The Y. lipolytica YB 423-12 strain produced 12.32 ± 1.54 U/mL (lipase activity) of lipase on hazelnut oil press cake medium supplemented with glucose. The best substrate for citric acid production was found to be borage oil, with an output of 5.34 ± 0.94 g/L. The biotechnological production of valuable metabolites such as single-cell oil, lipase, and citric acid could be achieved by using these wastes and low-cost substrates with this strain. Furthermore, the cost of the bio-process could also be significantly reduced by the utilization of various low-cost raw materials, residues, wastes, and renewable resources as substrates for this yeast.