Gustavo Davila-Vazquez

High removal of chemical and biochemical oxygen demand from tequila vinasses by using physicochemical and biological methods

The goal of this research is to find a more effective treatment for tequila vinasses (TVs) with potential industrial application in order to comply with the Mexican environmental regulations. TVs are characterized by their high content of solids, high values of biochemical oxygen demand (BOD 5), chemical oxygen demand (COD), low pH and intense colour; thus, disposal of untreated TVs severely impacts the environment. Physicochemical and biological treatments, and a combination of both, were probed on the remediation of TVs. The use of alginate for the physicochemical treatment of TVs reduced BOD 5 and COD values by 70.6% and 14.2%, respectively. Twenty white-rot fungi (WRF) strains were tested in TV-based solid media. Pleurotus ostreatus 7992 and Trametes trogii 8154 were selected due to their ability to grow on TV-based solid media. Ligninolytic enzymes’ production was observed in liquid cultures of both fungi. Using the selected WRF for TVs’ bioremediation, both COD and BOD 5 were reduced by 88.7% and 89.7%, respectively. Applying sequential physicochemical and biological treatments, BOD 5 and COD were reduced by 91.6% and 93.1%, respectively. Results showed that alginate and selected WRF have potential for the industrial treatment of TVs.

Iron effect on the fermentative metabolism of Clostridium acetobutylicum ATCC 824 using cheese whey as substrate

Butanol is considered a superior liquid fuel that can replace gasoline in internal combustion engines. It is produced by acetone-butanol-ethanol (ABE) fermentation using various species of solventogenic clostridia. Performance of ABE fermentation process is severely limited mostly by high cost of substrate, substrate inhibition and low solvent tolerance; leading to low product concentrations, low productivity, low yield, and difficulty in controlling culture metabolism. In order to decrease the cost per substrate and exploit a waste generated by dairy industry, this study proposes using cheese whey as substrate for ABE fermentation. It was observed that the addition of an iron source was strictly necessary for the cheese whey to be a viable substrate because this metal is needed to produce ferredoxin, a key protein in the fermentative metabolism of Clostridium acetobutylicum serving as a temporary electron acceptor. Lack of iron in the cheese whey impedes ferredoxin synthesis and therefore, restricts pyruvate-ferredoxin oxidoreductase activity leading to the production of lactic acid instead of acetone, butanol and ethanol. Moreover, the addition of FeSO4 notably improved ABE production performance by increasing butanol content (7.13 ± 1.53 g/L) by 65% compared to that of FeCl3 (4.32 ± 0.94 g/L) under the same fermentation conditions.

Use of agave bagasse for production of an organic fertilizer by pretreatment with Bjerkandera adusta and vermicomposting with Eisenia fetida.

ABSTRACT Agave tequilana Weber is used in tequila and fructans production, with agave bagasse generated as a solid waste. The main use of bagasse is to produce compost in tequila factories with a long traditional composting that lasts 6–8 months. The aim of this study was to evaluate the degradation of agave bagasse by combining a pretreatment with fungi and vermicomposting. Experiments were carried out with fractionated or whole bagasse, sterilized or not, subjecting it to a pretreatment with Bjerkandera adusta alone or combined with native fungi, or only with native bagasse fungi (non-sterilized), for 45 days. This was followed by a vermicomposting with Eisenia fetida and sewage sludge, for another 45 days. Physicochemical parameters, lignocellulose degradation, stability and maturity changes were measured. The results indicated that up to 90% of the residual sugars in bagasse were eliminated after 30 days in all treatments. The highest degradation rate in pretreatment was observed in non-sterilized, fractionated bagasse with native fungi plus B. adusta (BNFns) (71% hemicellulose, 43% cellulose and 71% lignin) at 45 days. The highest total degradation rates after vermicomposting were in fractionated bagasse pre-treated with native fungi (94% hemicellulose, 86% cellulose and 91% lignin). However, the treatment BNFns showed better maturity and stability parameters compared to that reported for traditional composts. Thus, it seems that a process involving vermicomposting and pretreatment with B. adusta could reduce the degradation time of bagasse to 3 months, compared to the traditional composting process, which requires from 6 to 8 months.

Presence and diversity of arbuscular mycorrhizal fungi in soil regularly irrigated with vinasses

The application of organic waste products, such as vinasses to the soil is a common practice in different countries. Vinasses are a residual liquid generated during various processes such as ethanol production and beverages distillation. However, little is known about how the vinasses affect the content and species distribution of arbuscular mycorrhizal fungi (AMF) in soils irrigated with vinasses. The aim of this research was to determine the presence, spore density and taxonomic identification of AMF to assess in vinasses irrigated (VS) and unirrigated soils (CS). Sixteen species were identified in irrigated and unirrigated soils, with a predominance of Acaulospora mellea, A. scrobiculata, Funneliformis geosporum, F. mosseae and Paraglomus occultum. Only Clareidoglomus etunicatum, Septoglomus constrictum, and Racocetra gregaria were found in VS, while A. morrowiae and Scuttelospora reticulate were only found in CS. The AMF abundance, root colonization, richness and biodiversity indices were not affected by vinasses application. It was found that irrigation of soil with vinasses seemed to have only a limited effect on AMF. To our knowledge, this is the first description of the species of AMF present in soil frequently irrigated with vinasse. This study could serve as a base for further investigations into the effect of vinasse on the soil microbial community and crop yields.