Contribution to the study of the alteration of lipase activity of Candida rugosa by ions and buffers

Sustainable Lipase Production by Diutina rugosa NRRL Y-95 Through a Combined Use of Agro-Industrial Residues as Feedstock

The potential use of alternative culture media towards the development of a sustainable bioprocess to produce lipases by Diutina rugosa is clearly demonstrated. First, a synthetic medium containing glucose, peptone, yeast extract, oleic acid, and ammonium sulfate was proposed, with lipase activity of 143 U/L. Then, alternative culture media formulated with agro-industrial residues, such as molasses, corn steep liquor (CSL), and olive mill waste (OMW), were investigated. An experimental design was conducted, and only CSL concentration was found to have a positive effect in lipase production. The highest lipase activity (561 U/L) was produced on a mixture of molasses (5 g/L), CSL (6 g/L), OMW (0.5% v/v), 0.5 g/L of ammonium sulfate, and 3 g/L of peptone at 24 h of cultivation. Lipase production was also carried out in a 1-L bioreactor leading to a slightly higher lipase activity at 24 h of cultivation. The semi-purified enzyme exhibits an optimum temperature and pH of 40 °C and 7.0, respectively. Finally, the media cost per unit of lipase produced (UPC) was influenced by the medium components, specially by the inducer used. The lowest UPC was obtained when the agro-industrial residues were combined and used at the improved concentrations.

Cross-linked enzyme aggregates (CLEAs) of selected lipases: a procedure for the proper calculation of their recovered activity

In the last few years, synthesis of carrier-free immobilized biocatalysts by cross-linking of enzyme aggregates has appeared as a promising technique. Cross-linked enzyme aggregates (CLEAs) present several interesting advantages over carrier-bound immobilized enzymes, such as highly concentrated enzymatic activity, high stability of the produced superstructure, important production costs savings by the absence of a support, and the fact that no previous purification of the enzyme is needed. However, the published literature evidences that a) much specific non-systematic exploratory work is being done and, b) recovered activity calculations in CLEAs still need to be optimized. In this context, this contribution presents results of an optimized procedure for the calculation of the activity retained by CLEAs, based on the comparison of their specific activity relative to their free enzyme counterparts. The protocol implies determination of precipitable protein content in commercial enzyme preparations through precipitation with ammonium sulphate and a protein co-feeder. The identification of linear ranges of activity versus concentration/amount of protein in the test reaction is also required for proper specific activity determinations. By use of mass balances that involve the protein initially added to the synthesis medium, and the protein remaining in the supernatant and washing solutions (these last derived from activity measurements), the precipitable protein present in CLEAs is obtained, and their specific activity can be calculated. In the current contribution the described protocol was applied to CLEAs of Thermomyces lanuginosa lipase, which showed a recovered specific activity of 11.1% relative to native lipase. The approach described is simple and can easily be extended to other CLEAs and also to carrier-bound immobilized enzymes for accurate determination of their retained activity.

Effect of Additives and Process Variables on Enzymatic Hydrolysis of Macauba Kernel Oil (Acrocomia aculeata)

This work investigates the production of free fatty acids (FFAs) from the enzymatic hydrolysis of macauba kernel oil. Experiments evaluate the effect of different enzymes and the addition of salts, surfactants, and solvents to the reaction medium, as well as the effect of process variables. Results showed that FFA yields obtained for use of Lipozyme RM IM were higher than those obtained from Lipozyme TL IM and Lipozyme 435. The addition of salts and surfactants did not promote increased production of FFAs, while addingn-hexane and heptane to the reaction medium led to an increased reaction rate. It can be observed for the results that the temperature, water :  oil mass ratio, and enzyme percentage had positive effects on the FFA yield in the range of 35°C to 55°C, 1 :  20 to 1 :  2, and 1 to 15%, respectively, and that, from these limits, increases in these variables did not cause significant increase in FFA yields. The addition of buffer promoted an increase in yield FFAs, as well as the pH of the buffer, and it was reported that an agitation of 400 rpm resulted in the highest yields in the investigated range.

A method for lipase co-precipitation in a biodegradable protein matrix

This article presents a novel method for immobilization of active ingredients. The method is based on CO(2) aided active ingredient co-precipitation with glycinin, a biodegradable protein matrix from edible soybean protein. Glycinin precipitates abundantly under isoelectric conditions and serves as the matrix within which the active substance is trapped during the precipitation process. The enzyme lipase from Candida rugosa was successfully co-precipitated into the protein pellet to prove the principle. It was shown that the lipase within the co-precipitate retained lipase and esterase activity under different pH conditions. In some cases the activity was even higher than the activity of crude lipase, possibly due to the protective role of the matrix protein. Due to the retained lipase activity and food-grade quality of the binary precipitate, it has potential of being used in the food or pharmaceutical industry. Additional quality of the binary precipitate is the potentially significantly reduced downstream processing due to the fact that no organic solvents or precipitants were used in the precipitation process.

Altering the substrate specificity of Candida rugosa LIP4 by engineering the substrate-binding sites

Candida rugosa (formerly Candida cylindracea) lipase (CRL) is an important industrial enzyme that is widely used in biotechnological applications such as the production of fatty acids and the synthesis of various esters. CRL comprises at least seven isozymes (LIP1-LIP7), which share a similar amino acid sequence but with different specificities for substrates. Previously, LIP4 was reported to have higher esterase activity toward long acyl-chain ester and lower lipase activity toward triglycerides. A296 and V344 of LIP4 were predicted to play decisive roles in its substrate specificity. In this study, site-specific saturation mutagenesis has been employed to study the substrate specificity of LIP4. Point mutations were separately introduced into A296 and V344 positions using degenerate primer sets containing 32 codons to generate two libraries of variants. LIP4 variants were heterologously expressed in the yeast Pichia pastoris. A specific plate assay was used to identify lipase-producing P. pastoris clones in a medium containing tributyrin. LIP4 variants with high activity toward short fatty acyl-chain triglyceride (tributyrin) were screened. Specificity analysis and biochemical characterization indicated that the recombinant variants A296I, V344Q, and V344H had properties remarkably different from those of wild-type LIP4. All three variant enzymes had significantly higher specific activities toward tributyrin than LIP4. In addition to short-chain triglyceride, A296I and V344Q also improved hydrolytic activities of triglycerides toward medium- and long-chain triglycerides tested. The results suggested that A296 played an important role in lipase activity and high-temperature dependence of LIP4, whereas it had no effect on the chain-length specificity in lipolytic reaction. The V344 residue had a significant effect on the substrate chain-length specificity of LIP4.

Protein engineering and applications of Candida rugosa lipase isoforms

Commercial preparations of Candida rugosa lipase (CRL) are mixtures of lipase isoforms used for the hydrolysis and synthesis of various esters. The presence of variable isoforms and the amount of lipolytic protein in the crude lipase preparations lead to a lack of reproducibility of biocatalytic reactions. Purification of crude CRL improve their substrate specificity, enantioselectivity, stability, and specific activities. The expression of the isoforms is governed by culture or fermentation conditions. Unfortunately, the nonsporogenic yeast C. rugosa does not utilize the universal codon CTG for leucine; therefore, most of the CTG codons were converted to universal serine triplets by site-directed mutagenesis to gain expression of functional lipase in heterologous hosts. Recombinant expressions by multiple-site mutagenesis or complete synthesis of the lipase gene are other possible ways of obtaining pure and different CRL isoforms, in addition to culture engineering. Protein engineering of purified CRL isoforms allows the tailoring of enzyme function. This involves computer modeling based on available 3-D structures of lipase isoforms. Lid swapping and DNA shuffling techniques can be used to improve the enantioselectivity, thermostability, and substrate specificity of CRL isoforms and increase their biotechnological applications. Lid swapping can result in chimera proteins with new functions. The sequence of the lid can affect the activity and specificity of recombinant CRL isoforms. Candida rugosa lipase is toxicologically safe for food applications. Protein engineering through lid swapping and rationally designed site-directed mutagenesis will continue to lead to the production of CRL isoforms with improved catalytic power, thermostability, enantioselectivity, and substrate specificity, while providing evidence for the mechanisms of actions of the various isoforms.

Multiple mutagenesis of non-universal serine codons of the Candida rugosa LIP2 gene and biochemical characterization of purified recombinant LIP2 lipase overexpressed in Pichia pastoris

The 17 non-universal serine codons (CTG) in the Candida rugosa LIP2 gene have been converted into universal serine codons (TCT) by overlap extension PCR-based multiple site-directed mutagenesis. An active recombinant LIP2 lipase was overexpressed in Pichia pastoris and secreted into the culture medium. The recombinant LIP2 showed distinguishing catalytic activities when compared with recombinant LIP4 and commercial C. rugosa lipase. The purified enzyme showed optimum activity at pH 7 and a broad temperature optimum in the range 30-50 degrees C. The enzyme retained 80% of residual activity after being heated at 70 degrees C for 10 min. Recombinant LIP2 demonstrated high esterase activity towards long-chain (C12-C16) p-nitrophenyl esters. Tributyrin was the preferred substrate among all triacylglycerols tested for lipolysis. Among cholesteryl esters, LIP2 showed highest lipolytic activity towards cholesteryl laurate. The esterification of myristic acid with alcohols of various chain lengths showed that the long-chain n-octadecanol (C18) was the preferred substrate. In contrast, the esterification of n-propanol with fatty acids of various chain lengths showed that the short-chain butyric acid was the best substrate. From comparative modelling analysis, it appears that several amino acid substitutions resulting in greater hydrophobicity in the substrate-binding site might play an important role in the substrate specificity of LIP2.

Design, total synthesis, and functional overexpression of the Candida rugosa lip1 gene coding for a major industrial lipase

The dimorphic yeast Candida rugosa has an unusual codon usage that hampers the functional expression of genes derived from this yeast in a conventional heterologous host. Commercial samples of C. rugosa lipase (CRL) are widely used in industry, but contain several different isoforms encoded by the lip gene family, among which the isoform encoded by the gene lip1 is the most prominent. In a first laborious attempt, the lip1 gene was systematically modified by site-directed mutagenesis to gain functional expression in Saccharomyces cerevisiae. As alternative approach, the gene (1647 bp) was completely synthesized with an optimized nucleotide sequence in terms of heterologous expression in yeast and simplified genetic manipulation. The synthetic gene was functionally expressed in both hosts S. cerevisiae and Pichia pastoris, and the effect of heterologous leader sequences on expression and secretion was investigated. In particular, using P. pastoris cells, the synthetic gene was functionally overexpressed, allowing for the first time to produce recombinant Lipl of high purity at a level of 150 U/mL culture medium. The physicochemical and catalytic properties of the recombinant lipase were compared with those of a commercial, nonrecombinant C. rugosa lipase preparation containing lipase isoforms.