Carlos Eduardo Hernández-Luna

Enhanced production of thermostable laccases from a native strain of Pycnoporus sanguineus using central composite design

The production of thermostable laccases from a native strain of the white-rot fungus Pycnoporus sanguineus isolated in Mexico was enhanced by testing different media and a combination of inducers including copper sulfate (CuSO4). The best conditions obtained from screening experiments in shaken flasks using tomato juice, CuSO4, and soybean oil were integrated in an experimental design. Enhanced levels of tomato juice as the medium, CuSO4 and soybean oil as inducers (36.8% (v/v), 3 mmol/L, and 1% (v/v), respectively) were determined for 10 L stirred tank bioreactor runs. This combination resulted in laccase titer of 143 000 IU/L (2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), pH 3.0), which represents the highest activity so far reported for P. sanguineus in a 10-L fermentor. Other interesting media resulting from the screening included glucose-bactopeptone which increased laccase activity up to 20 000 IU/L, whereas the inducers Acid Blue 62 and Reactive Blue 19 enhanced enzyme production in this medium 10 times. Based on a partial characterization, the laccases of this strain are especially promising in terms of thermostability (half-life of 6.1 h at 60 °C) and activity titers.概要研究目的优化获得血红密孔菌(P. sanguineus)的最佳培养基组成, 提高耐热漆酶的产量。创新要点获得了目前文献报道的最高水平的漆酶活力。研究方法通过单因素试验研究了不同培养基(番茄汁、 麦麸、 麦芽提取物和葡萄糖细菌蛋白胨培养基) 和不同组合诱导剂(大豆油、 阿魏酸、 没食子酸、 二甲基苯胺、 酸性蓝62 和活性蓝19 分别与硫酸铜组合诱导剂)对P. sanguineus 产耐热漆酶的影响。 在此基础上采用中心组合试验设计, 进一步研究了番茄汁培养基结合硫酸铜和大豆油组合诱导剂对P. sanguineus 产耐热漆酶的影响。 利用SAS10.0 和响应面分析方法对试验结果进行了统计分析和建立回归模型。重要结论通过中心组合设计优化得出P. sanguineus 产耐热漆酶的最优培养基条件: 以36.8%番茄汁为培养基, 以3 mmol/L 硫酸铜和1%大豆油作为组合诱导剂。 该条件下在10 L 搅拌槽生物反应器中漆酶活力达到了143 000 IU/L(2,2′-联氮双(3-乙基苯并噻唑啉-6-磺酸)为底物, pH 值为3.0)。

Immobilization of laccase of Pycnoporus sanguineus CS43

Laccase from Pycnoporus sanguineus CS43 was successfully immobilized onto Immobead-150 and Eupergit-C by covalent binding and by entrapment in LentiKats. The highest immobilization was onto Immobead-150 (97.1±1.2%) compared to the other supports, LentiKats (89±1.1%) and Eupergit-C (83.2±1.4%). All three immobilized enzyme systems showed increased thermostability and better mechanical properties than free laccase. Moreover, after 5 cycles of reuse of these systems, 90% of initial laccase activity was retained. Immobead-150 and LentiKats systems exhibited the highest efficiencies in removal of m-cresol under the combined actions of biodegradation and adsorption, while laccase entrapped in LentiKats showed a high ability for degradation of m-cresol within 24h. In addition, the typical Michaelis-Menten enzymatic model effectively described the kinetic profile of m-cresol degradation by the enzyme entrapped in LentiKats. Based on the results obtained in the present study, it can be established that the immobilized biocatalysts developed here possess significant potential for wastewater treatment.

Structural studies of two thermostable laccases from the white-rot fungus Pycnoporus sanguineus.

Laccases are enzymes that have the ability to catalyze the oxidation of a wide spectrum of phenolic compounds with the four-electron reduction of molecular oxygen to water. The active site of those proteins contains four copper ions, classified into three types. Laccases are interesting enzymes for study from the point of view of their structure, function and application because of their role in lignin degradation. Structural studies of two thermostable laccases produced by the strain Pycnoporus sanguineus CS43 (PsLacI and PsLacII) were performed. Both isoforms of PsLac show high thermal stability, at 60°C and 50°C, respectively, and they remained active at a high concentration of organic solvents. However, PsLacI has a higher thermal and pH stability and tolerance against inhibitors, and is a more efficient catalyst for ABTS and DMP (laccases substrate) than PsLacII. Based on the determined crystal structures we achieved insights into the structural factors relevant for the enzymatic properties of PsLacI and PsLacII. N-glycosylation site Asn354, which is very often present in structures of fungal laccases from other species, was not present in PsLac. This observation may be of particular significance due to the close distance between Asn354 and the substrate-binding pocket. This results in better access to the hydrophobic cavity for a particular substrate. Furthermore, we identified significant differences in the region of substrate-binding pocket, which confer PsLacI a markedly better performance than PsLacII.

Entamoeba histolytica: Soluble and membrane-associated neutral sphingomyelinase-C and other unidentified esterase activity

Sphingomyelinase (SMase) activity was measured in Entamoeba histolytica particulate and soluble subcellular fractions. The effects on SMase of incubation time, total protein concentration, pH, and several divalent cations were determined. SMase-C and other unidentified esterase activity were detected in soluble and particulate fractions. SMase-C was 94.5-96.0% higher than the unidentified esterase activity. Soluble and insoluble SMase-C specific activities increased with protein dose and incubation time. Soluble and insoluble SMase-C activities were maximum at pH 7.5 and were dependent on Mg(2+), Mn(2+), or Co(2+), and inhibited by Zn(2+), Hg(2+), Ca(2+), and EDTA. SMase-C was active in the pH range of 3-10 and its maximum activity was at pH 7.5. The soluble and insoluble SMases have remarkably similar physicochemical properties, strongly suggesting that E. histolytica has just one isoform of neutral SMase-C that had not been described before and might be essential for E. histolytica metabolism or virulence.

Effect of laccase from Trametes maxima CU1 on physicochemical quality of bread

Abstract The effect of laccase from Trametes maxima CU1 on physicochemical quality of bread was evaluated. Laccase treatment was 0.05% lower than the control in height, 0.33% higher in weight loss and reduced 17.71% the hardness of bread. In color, treatment with laccase was 18.72, 8.51 and 0.61% higher in L*, h, and C*, respectively. Chemical parameters of laccase treatment 12.00, 14.10 and 41.62% were higher than control in soluble arabinoxylans, protein and total phenols content, respectively. Based on the results obtained in the present study, laccase from T. maxima CU1 can be considered a good option for extraction and application as improver of the physicochemical quality of bread at industrial level.

Genetic and serologic surveillance of rotavirus with P[8] and P[4] genotypes in feces from children in the city of Chihuahua, northern Mexico.

Rotavirus vaccine was developed using the most prominent G and P genotypes circulating in children population. Therefore, severe gastroenteritis has been reduced around the world. This study investigated the G and P rotavirus genotypes circulating in children from two hospitals in the city of Chihuahua, Mexico. Additionally, polyclonal antibodies against Rotavirus Wa strain were used to determine their homotypic and heterotypic reactivity to both P[8] and P[4] genotypes. G1, G2, and G3 VP7 genotypes and P[8] and P[4] VP4 genotypes were detected in common and uncommon combinations as well as mixed infectious. The predominant combination was G1P[8]. Phylogenetic analysis of VP4 gene revealed the presence of P[8]-1 and P[8]-3 lineages of P[8] genotype and P[4]-5 lineage of P[4] genotype. All but five G1P[8] rotavirus were detected by polyclonal anti-Rotavirus Wa strain. Mutation analysis revealed differences in three of the four neutralizing epitopes previously reported to VP8* subunit of VP4 protein. Results of this study offer insights over genetic variants of field rotavirus that could be detected in a homotypic and heterotypic way by antibodies elicited to rotavirus with P[8] genotype. [Int Microbiol 2016; 19(1):27-32].

Increase of the antitumour efficacy of the biocompound IMMUNEPOTENT CRP by enzymatic treatment

ABSTRACT IMMUNEPOTENT CRP is a dialyzable leukocyte extract obtained from bovine spleen with immunomodulatory and antitumour properties; therefore, when administrated as an adjuvant therapy for cancer patients, it has increased their survival and quality of life. The bioavailability of any orally administered compound can be reduced due to gastrointestinal enzymes. In this study, we evaluated if IMMUNEPOTENT CRP is resistant to the treatment with different enzymes (proteases, nucleases, polysaccharide-degrading enzymes or lipase), using as parameters for biological activity measurement its in vitro antitumour and antioxidant properties and in vivo the antitumour effect of IMMUNEPOTENT CRP treated with proteinase K. In conclusion, we consider necessary to include the antioxidant and cytotoxic activity on the MCF-7 cancer cell line as parameters for the quantitative determination of biological activity or potency tests for batch release. Additionally, the results showed that different enzymatic treatments do not affect the antitumour and antioxidant activities of IMMUNEPOTENT CRP in vitro, suggesting that this product can be administered orally without any loss of biological activity. Furthermore, IMMUNEPOTENT CRP treatment with proteinase K increases the antitumour activity in vivo.

Sphingomyelinase Activity of Trichomonas vaginalis Extract and Subfractions

Trichomoniasis is one of the most common acute sexually transmitted curable diseases, and it is disseminated worldwide generating more than 170 million cases annually. Trichomonas vaginalis is the parasite that causes trichomoniasis and has the ability to destroy cell monolayers of the vaginal mucosa in vitro. Sphingomyelinases (SMase) are enzymes that catalyze the hydrolysis of sphingomyelin into ceramide and phosphorylcholine. Ceramide appears to be a second messenger lipid in programmed apoptosis, cell differentiation, and cell proliferation. Sphingomyelinase is probably a major source of ceramide in cells. Signal transduction mediated by ceramide leads cells to produce cytokine induced apoptosis during several inflammatory responses. SMase are also relevant toxins in several microorganisms. The main objective of this research is to identify SMase activity of T. vaginalis in the total extract (TE), P30, and S30 subfractions from brooked trophozoites. It was found that these fractions of T. vaginalis have SMase activity, which comes principally from P30 subfraction and was mainly type C. Enzymatic activity of SMase increased linearly with time and is pH dependent with two peaks by pH 5.5 and pH 7.5. The addition of manganese to the reaction mixture increased the SMase activity by 1.97.