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Mango fruits are easily damaged by knocking during harvest and transport, producing agro-industrial waste with high content of fermentable sugars. The aim of this work was to assess the production of bioethanol from residual Ataulfo (Mangifera indica L.) mango pulp, using vermicompost leachate as a nutritional supplement for ethanologenic yeast Saccharomyces cerevisiae during the fermentation process. Mango pulp was subjected to a dehydration process at 60 °C in order to preserve fermentable sugars. Moisture and ash content, total soluble solids (TSS), titratable acidity (TA), pH and total reducing sugar (TRS) concentration of the Ataulfo mango pulp were determined. Five treatments with different vermicompost leachate concentration (0%, 10%, 20%, 50% and 100%) were tested. The fermentation progress was evaluated by physicochemical characterization analysis (TSS and TRS) and accumulated production of CO2. Initial and final concentration of bioethanol was determined by HPLC. The highest bioethanol concentration of 44.67 ± 1.6 g/L was reached for treatment with 50% of vermicompost leachate. This result represents a viable option for using mango waste and vermicompost leachate as a renewable alternative for bioethanol production.

The present work shows the results of optimized alkaline pretreatment and enzymatic hydrolysis processes for the production of bioethanol from cocoa pod husk (CPH). Alkaline pretreatments were applied to evaluate the effect of NaOH concentration, residence time, and temperature using a Central Composite Design (CCD). SEM and XRD methodologies were used to study the structural characteristics of the solid fraction. Enzymatic hydrolysis assays were applied to optimize the enzyme (Cellic Ctec2, Novozyme) and solid loadings. The hydrolysate was subjected to fermentation using the yeast Saccharomyces cerevisiae Y2034. The results showed that the optimal condition for the alkaline pretreatment was 5% (w v−1) NaOH for 30 min at 120 °C, which increased the cellulose content of CPH from 27.68 ± 0.15 (untreated) to 57 ± 0.25%. SEM analysis showed changes in porosity and alterations in the biomass, while the XRD revealed an increase in crystallinity. The enzymatic hydrolysis was optimized to 10 FPU g−1 substrate and solid loading of 10% (w v−1), obtaining yields of 98.75%, equivalent to 66.80 g L−1 reducing sugars. During fermentation, 80.74% of reducing sugars were consumed, producing 18.06 g L−1 of ethanol in 24 h, corresponding to a theoretical yield of 51.45%. The results obtained show the potential of the use of cocoa pod husk as raw material for the production of bioethanol.

As Chiapas state, México, counts on an extensive hydrography with diverse nutrimental and climatic characteristics, it therefore allows isolating and identifying microalgae with bioenergetics potential. For this purpose, samples from 8 locations were collected, corresponding to 6 rivers, a wastewater and a springwater. The isolation of microalgae was developed for 4 weeks with 12:12 light/dark cycles. We demonstrated that the most efficient means for the isolation of microalgae of the hydrographic areas evaluated was the medium BG11 with 80.53% effectiveness. Of the microalgal consortium identified, 90% are composed of microalgae belonging to the class Chlorophycear. It was shown that another factor favouring the richness of morphotypes identified in the Santo Domingo River is associated with adequate concentrations of macroelements such as nitrates, nitrites, ammonium, phosphorus, sodium, potassium, magnesium and calcium at concentrations of 0.03 mg/l, 0.0006 mg/l, 0.08 mg/l, 0.03 mg/l, 62.93 mg/l, 5.46 mg/l, 34.52 mg/l and 48.78 mg/l respectively and microelements such as copper, zinc, iron, andmanganese at concentrations less than 0.2 mg/l in all microelements. The identified morphotypes, according to literature, have lipid contents ranging from 2 to 90%; this is of biotechnological importance for the production of biodiesel.

This paper proposes a method to determine bioethanol concentration that uses a pycnometer verified with a high performance liquid chromatography (HPLC) technique; it is a simple tool to determine the density of liquids for getting information about the ethanol concentration. The results showed that the sugar concentration affected the bioethanol concentration. A lower initial sugar concentration of 26.5 g/L generated higher yield of 45.3% sugar to bioethanol and a fractional or relative yield of 88.74%. Significance tests were used to compare the two experimental means, revealing that the pycnometer method and HPLC provide the same bioethanol concentration with joint variances of 2.269, 0.242, and 0.112 for 3 different tests with initial sugar concentrations of 26.486 g/L, 49.043 g/L, and 68.535 g/L, respectively. This study established and developed a methodology to determine bioethanol concentration from coffee mucilage by the proposed method.

The drying kinetics of mango were examined as a first step of pretreatment for biofuels production. This method exploits the potential of the carbohydrate present in the raw material, where the concentration for fermentation was adjusted to 20 g/L of reducing sugars. Dehydration was carried out by natural convection using a solar dryer. The solar dryer employed was made of transparent acrylic, and it had an internal volume of 0.125 m3. The dehydration was performed through natural convection. The dehydration achieved 95.6% moisture removal in 28 h and reached maximum temperatures of 52 °C and 56 °C, corresponding to first and second phases, respectively. The minimum temperature reached was 21 °C. The rate of drying was evaluated during the first stage, between 0 to 4 hours, with radiation maxima of 991 and 1014 W/m2 for that day. At the peak of radiation the drying rate was 0.060 g H2O/ g dry mass/ min.

A response surface methodology with 2k full factorial design was applied to obtain optimum conditions for bioethanol production using coffee mucilage (CM) as the substrate and Saccharomyces cerevisiae NRRL Y-2034 as the inoculum. CM is an agro-industrial residue mainly composed of simple sugars; the product yield and productivity process were analyzed with respect to the fermentation, pH, temperature, and the initial sugar concentration. Employing the following predicted optimum operational conditions attained the highest bioethanol production: pH 5.1, temperature 32 °C, and initial sugar concentration 61.8 g/L. The estimated bioethanol production was 15.02 g/L, and the experimental production was 16.29 g/L ± 0.39 g/L, with a bioethanol yield of 0.27 g/L and a productivity process of 0.34 g/Lh. Glycerol was the predominant byproduct of the fermentative metabolism of S. cerevisiae. The response surface methodology was successfully employed to optimize CM fermentation. In the fermentative processes with yeast, optimizing the conditions of the culture medium is needed to fully exploit the potential of the strains and maximize the production of bioethanol.