Ernesto Favela-Torres

The phenol-sulfuric acid method is the simplest and most frequently used procedure to determine the carbohydrate concentration. This method was developed to quantify purified or partially purified carbohydrates at concentrations below 0.1 g L⁻¹. However, its application in fermentation processes is limited due to the inherent characteristics of biological samples, which typically contain a variety of metabolites, high concentrations of macromolecules, and residual substrates. These factors can interfere with the quantification process. Thus, a modified phenol-sulfuric acid method was developed to control the reaction temperature, improving measurement accuracy and minimizing the impact of interferences. The results indicate that temperature, the phenol concentration, and reagent stability are the key parameters affecting absorbance measurement. The modified method involves a single premixed reagent in the reaction mixture instead of the conventional use of phenol and sulfuric acid. This approach allows for accurate and reliable measurement of monosaccharides, disaccharides, and polysaccharides with a concentration 20-fold higher (up to 1.75 g L⁻¹) than the conventional phenol-sulfuric acid method. For that, the proposed method involves the reduction of the dilutions in the biological samples, thereby enhancing the repeatability, reproducibility, and trueness of the experimental results.

The natural environment is an extraordinary reservoir of microorganisms that generate compounds with significant pharmaceutical relevance. Over the past decades, numerous companies have successfully exploited these microorganisms, primarily through submerged fermentation, to obtain antibiotics, enzymes, and other bioactive molecules. However, submerged fermentation sometimes presents limitations regarding oxygen transfer, production yields, compound stability, foaming, and environmental impact. Solid-state fermentation is a more sustainable alternative technology because it can valorize agro-industrial byproducts as culture media and produce bioactive compounds, contributing to a circular bioeconomy. The pharmaceutical industry is seeking solutions to decrease the costs of production processes and enhance process sustainability, and solid-state fermentation may provide exciting alternatives. However, challenges remain in scaling up, process control, and optimizing the recovery of bioactive compounds. This review highlights advances in bioactive compounds with potential pharmaceutical applications produced through solid-state fermentation, with particular emphasis on different classes, including antibiotics, biosurfactants, enzymes, polymers, vitamins, and aroma compounds. By addressing current limitations and showcasing innovative applications, solid-state fermentation is positioned as a viable complementary strategy for pharmaceutical bioprocesses. DOI: https://doi.org/10.54167/tch.v20i1.2152

Water hyacinth is an invasive weed that can valorize through the production of hydrolytic enzymes via solid-state culture. This study explores the application of Trichoderma harzianum in producing xylanases and endoglucanases on water hyacinth beds. Laboratory-scale packed-bed column bioreactors (PBCBs) with a capacity of 8 grams of dry mass (g_dm) were used to evaluate the effects of temperature (28–36 °C) and initial moisture content (65–80%) on microbial growth and enzyme production. High yields of biomass and enzymes were produced at 30 °C. Moreover, xylanase activity was enhanced in cultures with a moisture content of 65% (~71.24 U/g_dm), and endoglucanase activity at 75–80% moisture (~20.13 U/g_dm). The operational conditions identified for xylanase production were applied to 6 L bench-scale cross-flow internally stirred bioreactors, packed to 40% capacity with 450 g_dm. Two stirring regimes were tested: intermittent and continuous. The results showed that continuous stirring promotes both microbial growth and xylanase activity. In fact, xylanase activity in continuous stirring conditions was comparable to that achieved in PBCBs. Consequently, continuous stirring enables a 56-fold increase in bioreactor capacity without compromising xylanase production. The approaches developed in this study can support the design of large-scale bioprocesses for the valorization of water hyacinth.

Accurate quantification of spore concentration is essential in producing, analyzing, and applying diverse biotechnological products. Typically, spore concentration is estimated using a Neubauer hemocytometer, which is labor-intensive, time-consuming, and often imprecise. Methods based on spore optical properties can be explored as an alternative to using the Neubauer hemocytometer, improving the practicality and precision of analysis. This study aimed to establish the analysis conditions for quantifying the spore concentration using spectrophotometry and colorimetry (using L*a*b color space). For this study, spores from entomopathogenic fungi Beauveria bassiana, Hirsutella thompsonii, Cordyceps fumosorosea, Cordyceps javanica, Akanthomyces dipterigenus, Metarhizium acridum, Metarhizium anisopliae, and Metarhizium robertsii were produced and analyzed. The results indicate that both spectrophotometry and colorimetry analysis accurately estimate spore concentration. The quantification ranges achieved with both methods directly depend on the spore volume. Spores with a 15 µm³ or less volume exhibit a wider quantification range than those with larger volumes. Moreover, the L*a*b* color space analysis allows quantifying spores in a concentration range from 4.5 × 10⁶ to 3 × 10⁸ spores/mL, which is wider than the range obtainable through spectrophotometry. This extended concentration range provided by colorimetry offers a practical advantage for producing and applying entomopathogenic fungi spores.

BACKGROUND: Lactic acid (LA) is used in various industries and is produced mainly through lactic acid fermentation (LAF). The high cost of glucose, a common substrate, is a major challenge for LA production. Alternatives like fructans from agave are being explored for this purpose, including the production of probiotic beverages using the sap of agave leaves wasted in the field. This study aims to compare the kinetics of LA fermentation using agave fructans and glucose to identify the kinetic factors to be optimize for future use of this process.RESULTS: The study found that direct fructan fermentation by Lactobacillus bulgaricus delbrueckii (LDF) and Lactobacillus casei (LCF) achieved approximately half the productivity (P = 0.50, 0.59 gL⁻¹/h) as compared to glucose fermentation with the same strains (P = 0.92, 1.33 gL⁻¹/h) apparently because of the delay of fructan hydrolysis. The number of Colony Forming Units (CFU) increased following a logistic function, with a rapid decay observed for pH < 4, following first‐order kinetics. Despite the decay, CFU levels remained above 1E7 CFU/mL. This finding could be useful to produce probiotic beverages using agave leaves as a fermentation broth.CONCLUSION: The LAB strains, Lacticaseibacillus casei NRRL B‐441 (LC) and Lactobacillus delbrueckii bulgaricus NRRL B‐763 (LD), efficiently utilize commercial agave fructans as the primary carbon source, converting them into LA without prior hydrolysis. Fermentation productivity using fructans was approximately half of that obtained with glucose. This supports using agave fructans and sap for innovative lactic acid fermentations, including probiotic beverages. © 2025 Society of Chemical Industry (SCI).

A new machine for decortication of residual leaves of Agave salmiana was developed, yielding, juice (43 ± 6 %), wet pulp (25 ± 3 %), and wet fiber (18 ± 4 %) with an overall 86 ± 2 % recovery. Production of lactic acid (LA) and acetic acid (AA) in micro silages of wet agave pulp were assessed together with the evolution of lactic acid bacteria (LAB) and mesophile bacteria (MB) populations. LA spontaneous fermentation was followed by a two stage first order kinetics model (R2 = 0.89), At the start (pH = 5) MB population was 100 times higher than LAB = 1xE8 CFU/g. Fermentation peak was reached at 11 days when pH = 4, LA = 119 g/kg, LAB = 4xE9 CFU/g, and MB = 1xE8 CFU/g showing that LAB overgrew MB. Average AA values were negligible during the first month. After two months, LA and AA titers were 80 and 40 g/kg, respectively. Pasteurized pulp with LAB < 1E2 CFU/kg showed, significant LAB growth after one week of silage (3xE7 CFU/g). Inoculation of pasteurized pulp by selected LAB strains produced lower counts (8xE9 CFU/g) as compared to spontaneous fermentations (9xE10 CFU/g). Hence, spontaneous agave pulp fermentation is a reliable process for conservation of agave pulp and seems worth scaling-up as the basis for ruminant production in the dry lands of Central Mexico. It remains to develop the utilization of the juice and fiber fractions of A. salmiana as the basis for new biochemical and textile industries.

Filamentous fungi are widely used in industry to produce enzymes, organic acids, and secondary metabolites. Neurospora crassa has gained attention due to its flexibility for easy genetic manipulation, fast growth, and non-pathogenic characteristics. This study evaluated the growth of N. crassa and invertase production in submerged culture (SC) and solid-state culture (SSC) using pine sawdust (SSC-PS) and polyurethane foam (SSC-PUF) as supports. Modified Vogel's medium with initial sucrose concentrations of 1.5%, 3%, and 5% was used. The specific and maximum CO2 production rates were higher in SSC than SC, particularly with SSC-PS. Protein and invertase production were higher in SSC, with SSC-PS demonstrating the highest sucrose concentration as the inducer and carbon source. The water-holding capacity (WHC) of SSC-PUF was approximately 25 times higher than that of SSC-PS, facilitating a more productive process. SSC-PUF enables higher biomass growth, protein, and invertase production than SC. Moreover, using inert supports, such as PUF, allows the correct substrates and product assessment without interferences due to the chemical composition and heterogeneity of conventional agroindustrial by-products, such as PS.

La producción de nopal verdura es una actividad estratégica en México. El nopal es resistente a enfermedades e inclemencias climatológicas; sin embargo, es susceptible al ataque de diversos insectos. Entre ellos, el Picudo del nopal (Cactophagus spinolae) es potencialmente dañino para la planta y es combatido con sustancias químicas poco amigables con el medio ambiente. Por lo que, como alternativa para proteger a las plantas de infestaciones de Picudo, se evaluó el uso de Metarhizium robertsii como un agente de control biológico. A partir de la dosificación de esporas, el microorganismo mostró capacidad para disminuir la población de Picudos en condiciones de laboratorio y en campo abierto. Lo anterior demuestra que M. robersii puede utilizarse como agente de control biológico contra el Picudo del nopal. Con base en lo anterior, se podrá generar un paquete tecnológico para la producción y aplicación de altas cantidades de esporas de M. robertsii para el control biológico de Picudo del nopal con un enfoque sustentable.