Whole-cell biocatalysts for biodiesel fuel production

Conversion of lipid from food waste to biodiesel

Depletion of fossil fuels and environmental problems are encouraging research on alternative fuels of renewable sources. Biodiesel is a promising alternative fuel to be used as a substitute to the petroleum based diesel fuels. However, the cost of biodiesel production is high and is attributed mainly to the feedstock used which leads to the investigation of low cost feedstocks that are economically feasible. In this paper, we report on the utilization of lipid obtained from food waste as a low-cost feedstock for biodiesel production. Lipid from food waste was transesterified with methanol using base and lipase as catalysts. The maximum biodiesel yield was 100% for the base (KOH) catalyzed transesterification at 1:10M ratio of lipid to methanol in 2h at 60°C. Novozyme-435 yielded a 90% FAME conversion at 40°C and 1:5 lipid to methanol molar ratio in 24h. Lipid obtained from fungal hydrolysis of food waste is found to be a suitable feedstock for biodiesel production.

Two-step biocatalytic process using lipase and whole cell catalysts for biodiesel production from unrefined jatropha oil

OBJECTIVE

To avoid lipase deactivation by methanol in the enzymatic transesterification process, a two-step biocatalytic process for biodiesel production from unrefined jatropha oil was developed.

RESULTS

Unrefined jatropha oil was first hydrolyzed to free fatty acids (FFAs) by the commercial enzyme Candida rugosa lipase. The maximum yield achieved of FFAs 90.3% at 40 °C, water/oil ratio 0.75:1 (v/v), lipase content 2% (w/w) after 8 h reaction. After hydrolysis, the FFAs were separated and converted to biodiesel by using Rhizopus oryzae IFO4697 cells immobilized within biomass support particles as a whole-cell biocatalyst. Molecular sieves (3 Å) were added to the esterification reaction mixture to remove the byproduct water. The maximum fatty acid methyl ester yield reached 88.6% at 35 °C, molar ratio of methanol to FFAs 1.2:1, molecular sieves (3 Å) content 60% (w/w) after 42 h. In addition, both C. rugosa lipase and R. oryzae whole cell catalyst in the process showed excellent reusability, retaining 89 and 79% yields, respectively, even after six batches of reactions.

CONCLUSION

This novel process, combining the advantages of enzyme and whole cell catalysts, saved the consumption of commercial enzyme and avoid enzyme deactivation by methanol.

Preparation of immobilized whole cell biocatalyst and biodiesel production using a packed-bed bioreactor

Rhizopus oryzae NBRC 4697 was selected from among promising candidates as a biocatalyst for biodiesel production. This microorganism was immobilized on to polyurethane foam coated with activated carbon for reuse, and, for biodiesel production. Vacuum drying of the immobilized cells was found to be more efficient than natural or freeze-drying processes. Although the immobilized cells were severely inhibited by a molar ratio of methanol to soybean oil in excess of 2.0, stepwise methanol addition (3 aliquots at 24-h feeding intervals) significantly prevented methanol inhibition. A packed-bed bioreactor (PBB) containing the immobilized whole cell biocatalyst was then operated under circulating batch mode. Stepwise methanol feeding was used to mitigate methanol inhibition of the immobilized cells in the PBB. An increase in the feeding rate (circulating rate) of the reaction mixture barely affected biodiesel production, while an increase in the packing volume of the immobilized cells enhanced biodiesel production noticeably. Finally, repeated circulating batch operation of the PBB was carried out for five consecutive rounds without a noticeable decrease in the performance of the PBB for the three rounds.

Short-chain flavor ester synthesis in organic media by an E. coli whole-cell biocatalyst expressing a newly characterized heterologous lipase

Short-chain aliphatic esters are small volatile molecules that produce fruity and pleasant aromas and flavors. Most of these esters are artificially produced or extracted from natural sources at high cost. It is, however, possible to 'naturally' produce these molecules using biocatalysts such as lipases and esterases. A gene coding for a newly uncovered lipase was isolated from a previous metagenomic study and cloned into E. coli BL21 (DE3) for overexpression using the pET16b plasmid. Using this recombinant strain as a whole-cell biocatalyst, short chain esters were efficiently synthesized by transesterification and esterification reactions in organic media. The recombinant lipase (LipIAF5-2) showed good affinity toward glyceryl trioctanoate and the highest conversion yields were obtained for the transesterification of glyceryl triacetate with methanol. Using a simple cetyl-trimethylammonium bromide pretreatment increased the synthetic activity by a six-fold factor and the whole-cell biocatalyst showed the highest activity at 40°C with a relatively high water content of 10% (w/w). The whole-cell biocatalyst showed excellent tolerance to alcohol and short-chain fatty acid denaturation. Substrate affinity was equally effective with all primary alcohols tested as acyl acceptors, with a slight preference for methanol. The best transesterification conversion of 50 mmol glyceryl triacetate into isoamyl acetate (banana fragrance) provided near 100% yield after 24 hours using 10% biocatalyst loading (w/w) in a fluidized bed reactor, allowing recycling of the biocatalyst up to five times. These results show promising potential for an industrial approach aimed at the biosynthesis of short-chain esters, namely for natural flavor and fragrance production in micro-aqueous media.

Entrapment in polymeric material of resting cells of Aspergillus flavus with lipase activity. Application to the synthesis of ethyl laurate

The Aspergillus flavus lipase activity was improved by entrapment in polymeric acrylates. Free and entrapped resting cells were used in both packed-bed and batch reactors to prepare natural ethyl laurate.

A novel and robust recombinant Pichia pastoris yeast whole cell biocatalyst with intracellular overexpression of a Thermomyces lanuginosus lipase: preparation, characterization and application in biodiesel production

A novel and robust recombinant Pichia pastoris yeast whole cell catalyst (WCC) with functional intracellular expression of Thermomyces lanuginosus lipase (Tll) was constructed and characterized for biodiesel production from waste cooking oils. This permeabilized WCC was able to convert waste cooking oils to biodiesel with 82% yield within 84 h at 6% dosage whole cells. The WCC showed two fold catalytic activity of 0.73 U/mg DCW compared to its commercial counterpart Lipozyme TLIM (immobilized Tll). Short chain alcohol tolerance of this WCC was significantly improved compared to Lipozyme TLIM. This beneficial property enabled it to catalyze biodiesel production efficiently with one step addition of methanol. The reusability of this biocatalyst retained 78% activity after three batch cycles. This easily prepared and cost-effective WCC showed better catalytic performance than Lipozyme TLIM with respect to biodiesel yield and productivity, thus suggesting a promising cost-effective biocatalyst for biodiesel production.

Biocatalysis for biobased chemicals

The design and development of greener processes that are safe and friendly is an irreversible trend that is driven by sustainable and economic issues. The use of Biocatalysis as part of a manufacturing process fits well in this trend as enzymes are themselves biodegradable, require mild conditions to work and are highly specific and well suited to carry out complex reactions in a simple way. The growth of computational capabilities in the last decades has allowed Biocatalysis to develop sophisticated tools to understand better enzymatic phenomena and to have the power to control not only process conditions but also the enzyme's own nature. Nowadays, Biocatalysis is behind some important products in the pharmaceutical, cosmetic, food and bulk chemicals industry. In this review we want to present some of the most representative examples of industrial chemicals produced in vitro through enzymatic catalysis.

Application of the adhesive bacterionanofiber AtaA to a novel microbial immobilization method for the production of indigo as a model chemical

The toluene-degrading bacterium Acinetobacter sp. Tol 5 shows high adhesiveness mediated by the bacterionanofiber protein AtaA, which is a new member of the trimeric autotransporter adhesin (TAA) family. In contrast to other reported TAAs, AtaA mediates the adhesion of Tol 5 to various abiotic surfaces ranging from hydrophobic plastics to hydrophilic glass and stainless steel. The expression of ataA in industrially relevant bacteria improves their adhesiveness and enables immobilization directly onto support materials. This represents a new method that can be alternated with conventional immobilization via gel entrapment and chemical bonding. In this study, we demonstrate the feasibility of this immobilizing method by utilizing AtaA. As a model case for this method, the indigo producer Acinetobacter sp. ST-550 was transformed with ataA and immobilized on a polyurethane support. The immobilized ST-550 cells were transferred directly to a reaction solution containing indole as the substrate. The immobilized ST-550 cells showed a faster indigo production rate at high concentrations of indole compared with planktonic ST-550 not expressing the ataA gene, implying that immobilization enhanced the tolerance of ST-550 to the substrate indole. As a result, the immobilized ST-550 produced fivefold higher levels of indigo than planktonic ST-550. These results proved that AtaA is useful for bacterial immobilization.

A highly productive, whole-cell DERA chemoenzymatic process for production of key lactonized side-chain intermediates in statin synthesis

Employing DERA (2-deoxyribose-5-phosphate aldolase), we developed the first whole-cell biotransformation process for production of chiral lactol intermediates useful for synthesis of optically pure super-statins such as rosuvastatin and pitavastatin. Herein, we report the development of a fed-batch, high-density fermentation with Escherichia coli BL21 (DE3) overexpressing the native E. coli deoC gene. High activity of this biomass allows direct utilization of the fermentation broth as a whole-cell DERA biocatalyst. We further show a highly productive bioconversion processes with this biocatalyst for conversion of 2-substituted acetaldehydes to the corresponding lactols. The process is evaluated in detail for conversion of acetyloxy-acetaldehyde with the first insight into the dynamics of reaction intermediates, side products and enzyme activity, allowing optimization of the feeding strategy of the aldehyde substrates for improved productivities, yields and purities. The resulting process for production of ((2S,4R)-4,6-dihydroxytetrahydro-2H-pyran-2-yl)methyl acetate (acetyloxymethylene-lactol) has a volumetric productivity exceeding 40 g L⁻¹ h⁻¹ (up to 50 g L⁻¹ h⁻¹) with >80% yield and >80% chromatographic purity with titers reaching 100 g L⁻¹. Stereochemical selectivity of DERA allows excellent enantiomeric purities (ee >99.9%), which were demonstrated on downstream advanced intermediates. The presented process is highly cost effective and environmentally friendly. To our knowledge, this is the first asymmetric aldol condensation process achieved with whole-cell DERA catalysis and it simplifies and extends previously developed DERA-catalyzed approaches based on the isolated enzyme. Finally, applicability of the presented process is demonstrated by efficient preparation of a key lactol precursor, which fits directly into the lactone pathway to optically pure super-statins.

Enzymatic biodiesel production: an overview of potential feedstocks and process development

The increased global demand for biofuels has prompted the search for alternatives to edible oils for biodiesel production. Given the abundance and cost, waste and nonedible oils have been investigated as potential feedstocks. A recent research interest is the conversion of such feedstocks into biodiesel via enzymatic processes, which have considerable advantages over conventional alkali-catalyzed processes. To expand the viability of enzymatic biodiesel production, considerable effort has been directed toward process development in terms of biodiesel productivity, application to wide ranges of contents of water and fatty acids, adding value to glycerol byproducts, and bioreactor design. A cost evaluation suggested that, with the current enzyme prices, the cost of catalysts alone is not competitive against that of alkalis. However, it can also be expected that further process optimization will lead to a reduced cost in enzyme preparation as well as in downstream processes.

New biotransformation process for production of the fragrant compound γ-dodecalactone from 10-hydroxystearate by permeabilized Waltomyces lipofer cells

A new biotransformation process for the production of the flavor lactone was developed by using permeabilized Waltomyces lipofer, which was selected as an efficient γ-dodecalactone-producing yeast among 10 oleaginous yeast strains. The optimal reaction conditions for γ-dodecalactone production by permeabilized W. lipofer cells were pH 6.5, 35°C, 200 rpm, 0.7 M Tris, 60 g/liter of 10-hydroxystearic acid, and 30 g/liter of cells. Under these conditions, nonpermeabilized cells produced 12 g/liter of γ-dodecalactone after 30 h, with a conversion yield of 21% (wt/wt) and a productivity of 0.4 g/liter/h, whereas permeabilized cells obtained after sequential treatments with 50% ethanol and 0.5% Triton X-100 produced 46 g/liter of γ-dodecalactone after 30 h, with a conversion yield of 76% (wt/wt) and a productivity of 1.5 g/liter/h. These values were 3.7- and 3.8-fold higher than those obtained using nonpermeabilized cells. These are the highest reported concentration, conversion yield, and productivity for the production of the bioflavor lactone.

Combined utilization of lipase-displaying Pichia pastoris whole-cell biocatalysts to improve biodiesel production in co-solvent media

Lipase-displaying whole cells appear to be efficient biocatalysts because of their low preparation costs and simple recycling procedure. The combined utilization of Candida antarctica lipase B (CALB) and Rhizomucor miehei lipase (RML), separately displayed on Pichia pastoris whole cells, to produce biodiesel in co-solvent media was investigated. A response surface methodology incorporating a D-optimal design was employed to obtain the optimum reaction conditions for methyl ester (ME) synthesis. The synergistic effect of the two displayed lipases and the use of tert-butanol and isooctane as the co-solvent media were found to significantly improve the transesterification reaction. Scaled-up reactions using various types of feedstock were carried out in a 0.5-l stirred reactor under optimum conditions, affording ME yields over 90% in 12h. Moreover, the ME yields remained above 85% after 20 repeated batch cycles. In conclusion, this biocatalyst affords a promising route to efficient biodiesel production.

Efficient Production of Biodiesel from Rapeseed Oil Deodorizer Distillate: One-Pot Esterification and Transesterfication with Compound Lipases

A novel concept and efficient method for producing biodiesel from rapeseed oil deodorizer distillate (RODD) was developed by using compound lipases for one-pot esterification of FFA and transesterification of triglyceride with methanol in a solvent-free system. Compound lipases Novozyme435 and immobilized Pseudomonas cepacia G63 at 1:1(wt/wt) gave FAME about 96% yield under optimal conditions, being better than that with single lipase or other compound lipases. Besides, the loss rate of vitamin E was 18% much lower than that of using chemical catalyst, which shows that the compound lipases Novozyme435 and immobilized P. cepacia G63 can be ideal catalysts for biodiesel production from rapeseed oil deodorizer distillate.

Improving lipase activity by immobilization and post-immobilization strategies

One important parameter for the application of lipase catalysts in chemical industries is the specific activity displayed towards natural or unnatural substrates. Different strategies to enhance the lipase activity have been described. The immobilization of lipases on hydrophobic supports by interfacial adsorption at low ionic strength permitted the hyper-activation of these enzymes by fixing the open conformation of the lipase on the hydrophobic support. Improvements of activity from 1.2- up to 20-fold with respect to the initial one have been observed for lipases from different sources. A second strategy was based on the presence of additives, in particular surfactants or ionic liquids, with hydrophobic character to enhance the activity of lipases immobilized on macroporous supports up to eightfold and even more than 100-fold in some cases for soluble lipases. Finally, a third strategy to improve the activity in immobilized lipases was based on a site-directed chemical modification of the protein by glycosylation on the enzyme N-terminal group or on a unique reactive cysteine of the enzyme by disulfide exchange using different tailor-made disulfide activated activated polymers.

Comparative analysis for the production of fatty acid alkyl esterase using whole cell biocatalyst and purified enzyme from Rhizopus oryzae on waste cooking oil (sunflower oil)

The petroleum fuel is nearing the line of extinction. Recent research and technology have provided promising outcomes to rely on biodiesel as the alternative and conventional source of fuel. The use of renewable source - vegetable oil constitutes the main stream of research. In this preliminary study, Waste Cooking Oil (WCO) was used as the substrate for biodiesel production. Lipase enzyme producing fungi Rhizopus oryzae 262 and commercially available pure lipase enzyme were used for comparative study in the production of Fatty Acid Alkyl Esters (FAAE). The whole cell (RO 262) and pure lipase enzyme (PE) were immobilized using calcium alginate beads. Calcium alginate was prepared by optimizing with different molar ratios of calcium chloride and different per cent sodium alginate. Entrapment immobilization was done for whole cell biocatalyst (WCB). PE was also immobilized by entrapment for the transesterification reaction. Seven different solvents - methanol, ethanol, n-propanol, n-butanol, iso-propanol, iso-butanol and iso-amyl alcohol were used as the acyl acceptors. The reaction parameters like temperature (30°C), molar ratio (1:3 - oil:solvent), reaction time (24 h), and amount of enzyme (10% mass ratio to oil) were also optimized for methanol alone. The same parameters were adopted for the other acyl acceptors too. Among the different acyl acceptors - methanol, whose reaction parameters were optimized showed maximum conversion of triglycerides to FAAE-94% with PE and 84% with WCB. On the whole, PE showed better catalytic converting ability with all the acyl acceptor compared to WCB. Gas chromatography analysis (GC) was done to determine the fatty acid composition of WCO (sunflower oil) and FAAE production with different acyl acceptors.

A facile whole-cell biocatalytic approach to regioselective synthesis of monoacylated 1-β-D-arabinofuranosylcytosine: influence of organic solvents

The lyophilized Pseudomonas fluorescens cell was an efficient alternative catalyst to enzymes for highly regioselective acylation of a polar nucleoside, 1-β-D-arabinofuranosylcytosine (ara-C). The cells showed an evident solvent dependence in the reaction. Among the tested solvents except for acetonitrile-pyridine, catalytic activity of the cells clearly increased with increasing the polarity of the organic solvents used. Among all the tested solvents both pure and binary, the best results were observed in isopropyl ether-pyridine system, in which the catalyst also showed good thermal and operational stabilities. For the biocataylsis in isopropyl ether-pyridine, the optimal isopropyl ether concentration, water content, acyl donor/ara-C ratio, biocatalyst dosage and reaction temperature were 30% (v/v), 4%, 45, 50mg/mL and 30 °C, respectively, under which the initial rate, yield and 5'-regioselectivity were 2.93 mM/h, 77.1% and 97.3%, respectively. The bacterial cells exhibited comparable 5'-regioselectivity to the expensive immobilized enzyme, which could also have environmental and cost advantages.

Whole-cell based solvent-free system for one-pot production of biodiesel from waste grease

A whole-cell based solvent-free system was developed for efficient conversion of waste grease to biodiesel via one-pot esterification and transesterification. By isolation and screening of lipase-producing strains from soil, Serratia marcescens YXJ-1002 was discovered for the biotransformation of grease to biodiesel. The lipase (SML) from this strain was cloned and expressed in Escherichia coli as an intracellular enzyme, showing 6 times higher whole-cell based hydrolysis activity than that of wild type strain. The recombinant cells were used for biodiesel production from waste grease in one-pot reactions containing no solvent with the addition of methanol in several small portions, and 97% yield of biodiesel (FAME) was achieved under optimized conditions. In addition, the whole-cell biocatalysts showed excellent reusability, retaining 74% productivity after 4 cycles. The developed system, biocatalyst, and process enable the efficient, low-cost, and green production of biodiesel from waste grease, providing with a potential industrial application.

Different strategies for hyperactivation of lipase biocatalysts

One important parameter for the application of lipase catalysts in chemical industries is the specific activity displayed towards natural or unnatural substrates. Different strategies to enhance the lipase activity have been described. The immobilization of lipases on hydrophobic supports by interfacial adsorption at low ionic strength permitted the hyperactivation of these enzymes by fixing the open conformation of the lipase on the hydrophobic support. Improvements of activity from 1.2- up to 20-fold with respect to the initial one have been observed for lipases from different sources.A second strategy was based on the presence of additives, in particular surfactants, with hydrophobic character to enhance the activity of lipases immobilized on macroporous supports up to 8 fold and even more than 100-fold in some cases for soluble lipases.Finally, a third strategy to improve the activity in lipases was based on a site-directed chemical modification of the protein on a unique reactive cysteine of the enzyme by disulfide exchange using different tailor-made activated polymers.