Low-performance diagnosis of covered anaerobic lagoons as a waste management strategy in the intensive dairy industry.

Covered anaerobic lagoons (CALs) are Latin America's main livestock waste treatment systems. Mexico has 680 CALs that present low biogas yields (0.05 m3 m-3 digester d-1) and low COD removal rates (< 60%). This work focused on diagnosing CAL´s low performance in dairy farms by determining and analyzing operational parameters. Seven CALs located in the main dairy basin of Mexico were analyzed. The sampling areas for each CAL were the supernatant, the active zone, settled sludge, and digester inlet and outlet. The variation of the process parameter values corroborated that CALs appeared stratified and not working as expected. The sludge zone, comprising 50-58% of total solids content and 1-15% of total CALs volume, showed an elemental compounds content suitable for organic fertilizer (340, 48, and 5 kg t-1 of C, N, and S, respectively). However, this zone contained, at least, 85% of the slowly hydrolysable material; the methanogenic potential was less than 87 mL CH4 g VS-1, and the C/N ratio ranged from 4.9 to 17, outside of the optimal range. The biogas produced did not exceed 60% of methane content and more than 3000 ppm of H2S. The sludge zone significantly influences the lagoon's dynamics since it is a nutrient sink. Furthermore, the lack of agitation is the leading cause for the low energy yield and the low removal of organic matter rate. This work provides valuable information to address the operational problems within the CALs improving our understanding that shall allow proposing reactivation alternatives.

Immobilization of phosphonium-based ionic liquid stationary phases extends their operative range to routine applications in the flavor, fragrance and natural product fields.

Phosphonium-based ionic liquids (ILs) have proven to be successful stationary phases (SPs) for gas chromatography (GC) in several fields of application because of their unique selectivity and good chromatographic properties. This study focuses on the use of two ILs as GC SPs that are based on the phosphonium derivatives trihexyl(tetradecyl)phosphonium chloride ([P66614+] [Cl-]), and trihexyl(tetradecyl)phosphonium bis[(trifluoromethyl)sulfonyl]imide ([P66614+][NTf2-]), which have previously been shown to be complementary in terms of chromatographic selectivity and retention. Their application in routine analysis has been limited by their lower maximum allowable operating temperatures (MAOT) (200 °C for the [P66614+][Cl-] IL and 180 °C for [P66614+][NTf2-]), which restricts their use to samples that consist of analytes with relatively high volatility. A previous study carried out in the Authors' laboratory focused on extending the use of the [P66614+][Cl-] IL SP to the analysis of samples with analytes of medium-to-low volatility by optimizing column characteristics and operative conditions. This study addresses the immobilization of both the [P66614+][Cl-] and [P66614+][NTf2-] ILs to the inner wall of fused silica columns to increase their MAOT under soft and hard reaction conditions. The resulting MAOT depended on more or less drastic immobilization conditions, and reached 220 °C for soft immobilization (So-Im) and 240 °C for hard immobilization (Ha-Im) in the [P66614+][Cl-] IL columns, and 200 °C for So-Im and 220° for Ha-Im in columns coated with the [P66614+] [NTf2-] IL. The influence of immobilization on the separation power and performance of all the columns has been evaluated using i) the Grob test, ii) a model mixture of 41 compounds of different polarity, structure, and with different organic functional groups representative of the flavor and fragrance field, iii) a standard mixture of 37 fatty acid methyl esters, iv) the peppermint essential oil, v) two mixtures of sesquiterpenic alcohols (farnesols and santalols), and vi) a standard mixture of 16 pesticides. These test samples were also used to demonstrate the complementarity of the two phosphonium-based IL SPs in terms of selectivity and retention.

Cost-effective optimized scleroglucan production by Sclerotium rolfsii ATCC 201126 at bioreactor scale. A quantity-quality assessment.

Exopolysaccharide (EPS) secretion by Sclerotium rolfsii ATCC 201126 in submerged cultures, already identified as high-osmolarity responsive, was assessed by reducing C-source without compromising EPS yields. A designed medium with 80 g sucrose L-1 (MOPT80) was tested at 3 L-bioreactor scale at different temperature, agitation, aeration and pH (uncontrolled vs. controlled) values. Optimal operative conditions (200 rpm, 28 °C, 0.5 vvm and initial pH -pHi- 4.5) were validated, as well as the possibility to work at pHi 5.5 to reduce biomass production. Purified EPSs produced in MOPT80 at optimal and other valid operative conditions exhibited refined grade (<1 % proteins and ash, 3-4 % reducing sugars, 87-99 % total sugars). EPS purity, MW and rheological parameters led to discourage pH controlled at 4.5. Relatively constant MW (6-8 × 106 Da) and outstanding viscosifying ability were found. Polyphasic EPS analysis (titre, purity, macromolecular features and rheological fitness) would support to properly select production conditions.