Biological Pretreatment of Mexican Caribbean Macroalgae Consortiums Using Bm-2 Strain (Trametes hirsuta) and Its Enzymatic Broth to Improve Biomethane Potential

The macroalgae consortium biomass in the Mexican Caribbean represents an emerging and promising biofuel feedstock. Its biological pretreatment and potential for energetic conversion to biomethane were investigated, since some macroalgae have hard cell walls that present an obstacle to efficient methane production when those substrates are used. It has been revealed by anaerobic digestion assays that pretreatment with a Bm-2 strain (Trametes hirsuta) isolated from decaying wood in Yucatan, Mexico was 104 L CH4 kg·VS−1; In fact, the fungal pretreatment produced a 20% increase in methane yield, with important amounts of alkali metals Ca, K, Mg, Na of 78 g/L, ash 35.5% and lignin 15.6%. It is unlikely that high concentrations of ash and alkali metals will produce an ideal feedstock for combustion or pyrolysis, but they can be recommended for a biological process

Laccase Gene Expression and Vinasse Biodegradation by Trametes hirsuta Strain Bm-2

Vinasse is the dark-colored wastewater that is generated by bioethanol distilleries from feedstock molasses. The vinasse that is generated from molasses contains high amounts of pollutants, including phenolic compounds and melanoindin. The goal of this work was to study the expression of laccase genes in the Trametes hirsuta strain Bm-2, isolated in Yucatan, Mexico, in the presence of phenolic compounds, as well as its effectiveness in removing colorants from vinasse. In the presence of all phenolic compounds tested (guaiacol, ferulic acid, and vanillic acid), increased levels of laccase-encoding mRNA were observed. Transcript levels in the presence of guaiacol were 40 times higher than those in the control. The lcc1 and lcc2 genes of T. hirsuta were differentially expressed; guaiacol and vanillin induced the expression of both genes, whereas ferulic acid only induced the expression of lcc2. The discoloration of vinasse was concomitant with the increase in laccase activity. The highest value of enzyme activity (2543.7 U/mL) was obtained in 10% (v/v) vinasse, which corresponded to a 69.2% increase in discoloration. This study demonstrates the potential of the Bm-2 strain of T. hirsuta for the biodegradation of vinasse

Vírus associado ao espessamento dos cladódios da pera espinhosa (Opuntia ficus-indica Mill.)

Symptoms putative to phytoplasmas and virus as yellowing, mosaic, proliferation and deformation of fruits and thickening of the cladodes of prickly pear have been observed in Nopaltepec, Estado de México. The objective of this investigation was to detect the presence of virus in samples of prickly pear showing thickening syndrome of the cladodes. The analysis of double-stranded RNA in prickly pear tissue whit the symptoms mentioned above revealed the presence of viral RNA. In symptomatic tissue, flexible rods of 950-1700 nm in length were observed with the aid of transmission electron microscopy. The virus was transmitted mechanically to Nicotiana tabacum var. Xanthi, N. glutinosa, N. occidentalis, N. benthamiana, Chenopodium quinoa, C. amaranticolor and Datura stramonium. Results from RT-PCR indicate that the particle does not correspond to TMV, neither to member of the Potyviridae family or species of the genus Potexvirus.   Sintomas putativos de fitoplasmas e vírus como amarelecimento, mosaico, proliferação e deformação de frutos e espessamento dos cladódios de pera espinhosa foram observados em Nopaltepec, Estado do México. O objetivo desta investigação foi detectar a presença de vírus em amostras de pera espinhosa mostrando síndrome de espessamento dos cladódios. A análise do RNA de fita dupla no tecido de pera espinhosa com os sintomas mencionados acima revelou a presença de RNA viral. No tecido sintomático, barras flexíveis de 950-1700 nm de comprimento foram observadas com o auxílio da microscopia eletrônica de transmissão. O vírus foi transmitido mecanicamente para Nicotiana tabacum var. Xanthi, N. glutinosa, N. occidentalis, N. benthamiana, Chenopodium quinoa, C. amaranticolor e Datura stramonium. Os resultados da RT-PCR indicam que a partícula não corresponde ao TMV, nem ao membro da família Potyviridae ou a espécies do gênero Potexvirus

Brosimum Alicastrum as a Novel Starch Source for Bioethanol Production

Ramon (Brosimum alicastrum) is a forest tree native to the Mesoamerican region and the Caribbean. The flour obtained from Ramon seeds is 75% carbohydrate, of which 63% is starch, indicating its potential as a novel raw material for bioethanol production. The objective of this study was to produce ethanol from Ramon flour using a 90 °C thermic treatment for 30 min and a native yeast strain (Candida tropicalis) for the fermentation process. In addition, the structure of the flour and the effects of pretreatment were observed via scanning electron microscopy. The native yeast strain was superior to the commercial strain, fermenting 98.8% of the reducing sugar (RS) at 48 h and generating 31% more ethanol than commercial yeast. One ton of flour yielded 213 L of ethanol. These results suggest that Ramon flour is an excellent candidate for ethanol production. This is the first report on bioethanol production using the starch from Ramon seed flour and a native yeast strain isolated from this feedstock. This alternative material for bioethanol production minimizes the competition between food and energy production, a priority for Mexico that has led to significant changes in public policies to enhance the development of renewable energies

Nematicidal Screening of Aqueous Extracts from Plants of the Yucatan Peninsula and Ecotoxicity

Active metabolites from plants are considered safer than synthetic chemicals for the control of plant-parasitic nematodes of the genus Meloidogyne. In the present work, 75 aqueous extracts (AEs) from different vegetative parts of 34 native plant species of the Yucatan Peninsula were evaluated against second-stage juveniles (J2s) of Meloidogyne incognita and M. javanica in microdilution assays. The highest mortality (M) against both Meloidogyne species was produced by the foliar AE from Alseis yucatanensis (M ≥ 94%) and Helicteres baruensis (M ≥ 77%) at 3% w/v after 72 h. Other active AEs at 3% were from the leaves of Croton itzaeus and stems of H. baruensis (M: 87–90%) on M. javanica and the stems of Annona primigenia and the leaves of Morella cerifera on M. incognita (M: 92–97%). The AEs from A. yucatanensis had the lowest LD50 against M. incognita (0.36% w/v), and against M. javanica (3.80% w/v). In an acute ecotoxicity assay of the most promising AEs using non-target earthworms (Eisenia fetida), the AE of A. yucatanensis had slight acute toxicity (LD50: 2.80% w/v), and the rest of the most active AEs were not ecotoxic. These tropical plants are potential candidates for further studies as biorational agents for controlling Meloidogyne species

Genetic Variability of Oil Palm in Mexico: An Assessment Based on Microsatellite Markers

Oil palm (Elaeis guineensis Jacq.) has become the largest source of vegetable oil in the world. It is known that all existing genotypes of this species are related, so their genetic variability is considered to be low. In Mexico, all oil palm plantations are located in the southeast of the country, and they are established with different origins seeds, which has caused poor yields and resulted in the need to establish a genetic improvement program. Therefore, in this study, the extent of genetic diversity among 151 oil palm accessions from all producing regions of Mexico was assessed with twenty simple sequence repeats (SSRs) and seven random amplified microsatellite (RAM) markers. The markers utilized proved to be useful in revealing high existing genetic variability, with a total of 1218 and 708 alleles detected and polymorphic information content (PIC) of 0.96 and 0.91 for RAM and SSR, respectively. The genetic distance among all accessions of oil palm collected ranged between 31% and 82% for similarity. Accessions from Tabasco and Veracruz presented the greatest and smallest genetic diversity, respectively. These results can allow breeding strategies to be established for the genetic improvement of this crop in Mexico

A Current Overview of the Papaya meleira virus, an Unusual Plant Virus

Papaya meleira virus (PMeV) is the causal agent of papaya sticky disease, which is characterized by a spontaneous exudation of fluid and aqueous latex from the papaya fruit and leaves. The latex oxidizes after atmospheric exposure, resulting in a sticky feature on the fruit from which the name of the disease originates. PMeV is an isometric virus particle with a double-stranded RNA (dsRNA) genome of approximately 12 Kb. Unusual for a plant virus, PMeV particles are localized on and linked to the polymers present in the latex. The ability of the PMeV to inhabit such a hostile environment demonstrates an intriguing interaction of the virus with the papaya. A hypersensitivity response is triggered against PMeV infection, and there is a reduction in the proteolytic activity of papaya latex during sticky disease. In papaya leaf tissues, stress responsive proteins, mostly calreticulin and proteasome-related proteins, are up regulated and proteins related to metabolism are down-regulated. Additionally, PMeV modifies the transcription of several miRNAs involved in the modulation of genes related to the ubiquitin-proteasome system. Until now, no PMeV resistant papaya genotype has been identified and roguing is the only viral control strategy available. However, a single inoculation of papaya plants with PMeV dsRNA delayed the progress of viral infection

Physical Characteristics of the Leaves and Latex of Papaya Plants Infected with the Papaya meleira Virus

Sticky disease, which is caused by Papaya meleira virus (PMeV), is a significant papaya disease in Brazil and Mexico, where it has caused severe economic losses, and it seems to have spread to Central and South America. Studies assessing the pathogen-host interaction at the nano-histological level are needed to better understand the mechanisms that underlie natural resistance. In this study, the topography and mechanical properties of the leaf midribs and latex of healthy and PMeV-infected papaya plants were observed by atomic force microscopy and scanning electron microscopy. Healthy plants displayed a smooth surface with practically no roughness of the leaf midribs and the latex and a higher adhesion force than infected plants. PMeV promotes changes in the leaf midribs and latex, making them more fragile and susceptible to breakage. These changes, which are associated with increased water uptake and internal pressure in laticifers, causes cell disruption that leads to spontaneous exudation of the latex and facilitates the spread of PMeV to other laticifers. These results provide new insights into the papaya-PMeV interaction that could be helpful for controlling papaya sticky disease