Our previous work has shown the technical and economic feasibility of the solid substrate anaerobic digestion (DASS) of municipal and non-hazardous industrial solid wastes. However, the anaerobic compost (AnC) quality for direct application as a soil amender or other alternative uses are issues that have received scarce attention. This research aimed at reviewing the advances made by our Group in two areas: anaerobic compost quality determination, and its post-treatment by aerobic composting. A factorial experiment 4×2×2 was run. The factors were feedstock type (4 mixtures of food waste, FW, and lignocellulosic fraction, LG: 100%FW, 67%FW-33%LG, 33%FW-67%LG and 100%LG or FS1, FS2, FS3 and FS4 respectively), temperature (35°C and 55°C), and mass retention time (MRT, 16 and 23 days). The LG fraction consisted of paper mill sludge cake. Anaerobic compost from DASS reactors operated at 23 day/35°C) was fed to lab scale semi-continuous aerobic composters (5 day and 10 day MRT, 35°C and 55°C). The AnC coming from feedstocks with increasing proportion of LG fraction (FS3 and FS4) gave the lowest chemical oxygen demand (COD), biochemical oxygen demand (BOD), volatile organic acids (VOA) and total ammonia nitrogen (TAN) concentrations in the extract and the highest germination indices (GI). The AnC from thermo- digesters showed a lower quality than those from mesophilic reactors (presumably associated to higher contents of VOA and TAN in the extracts), while AnC from digesters at 23 day-MRT had a better quality than those from reactors operated at 16-day-MRT. Overall, AnC generated in reactors fed with FS3 and FS4, at 35°C and 23 day-MRT showed the highest quality. Heavy metal concentrations in all the AnC were lower than the maximum levels indicated in USA and European compost quality standards. However, high total oxygen uptake (UAD), moderate-to-high concentrations of VOA and GIs under 60% indicated that the AnC was not suitable for direct use as a soil improver. Regarding the aerobic post-composting, operation at longer MRT (10 day) and 55°C gave aerobic composts of better quality than those coming from 5 day-MRT composters. Aerobic post-composting caused considerable reductions of TAN, VOA, UAD, immediate oxygen demand rate, and increased compost GI up to approximately 100%.

The influence of Triton X-100 on Beta vulgaris L. permeabilized cell culture viability, regrowth, and ability to produce betacyanines was evaluated in this study. A non-destructive method based on the analysis of images in the RGB (red, green, blue) system was developed to estimate betacyanines content. A treatment for 15 min with 0.7 mM Triton X-100 induced the release of 30% of betacyanines without loss of cell viability (>or=70%). After this permeabilization treatment, B. vulgaris cultures regrew normally, reaching a maximum biomass concentration of 48% higher than non-permeabilized cultures after 14 days of culture. Also, maximum betacyanines concentration was only 25% lower than that of non-permeabilized cultures.

Uncaria tomentosa cell suspension cultures were grown in a 2-L stirred tank bioreactor operating at a shear rate gamma(.)(avg)=86 s(-1). The cultures showed an early monophasic oxidative burst measured as H2O2 production (2.15 micromol H2O2 g(-1) dw). This response was followed by a transient production of monoterpenoid oxindole alkaloids (178 +/- 40 microg L(-1) at 24 h). At the stationary phase (144 h), the increase of the shear rate gamma(.)(avg) up to 150 s(-1) and/or oxygen tension up to 85% generated H2O2, restoring oxindole alkaloid production. U. tomentosa cells cultured in Erlenmeyer flasks also exhibited the monophasic oxidative burst but the H2O2 production was 16-fold lower and the alkaloids were not detected. These cells exposed to H2O2 generated in situ produced oxindole alkaloids reaching a maximum of 234 +/- 40 microg L(-1). A positive correlation was observed between the oxindole alkaloid production and the endogenous H2O2 level. On the other hand, addition of 1 microM diphenyleneiodonium (NAD(P)H oxidase inhibitor) or 10 microM sodium azide (peroxidases inhibitor) reduced both H2O2 production and oxindole alkaloids build up, suggesting that these enzymes might play a role in the oxidative burst induced by the hydrodynamic stress.

This study presents a protocol for the establishment of Prosopis laevigata cell suspension culture as a strategy to obtain an in vitro mesquite gum productive cell line. The callus used for this purpose was obtained with hypocotyls from 15-day-old plantlets, placed on Murashige-Skoog medium with two different plant growth regulators (PGRs), 2,4,5-trichlorophenoxy acetic acid (2,4,5-T; 5.0 lM) and kinetin (KIN; 5.0 lM). With this PGRs treatment, after four subcultures (30 days each) an exuded gum-like substance was observed on the callus surface. The growth kinetics of the cell suspension culture showed a specific cell growth rate (l) of 0.14 d -1 and doubling time (t d ) of 6.6 days, respectively. The gum-like substance from callus culture and the broth from cell suspension culture were subjected to chemical analysis and compared with the mesquite gum exuded from wild trees. Both, gum-like substance from callus culture and the broth from cell suspension culture showed the presence of Arabinogalactanproteins, and their polysaccharide fraction presented the same monosaccharides as those isolated from mesquite gum. In addition, the emulsifying properties of gum-like substance from callus culture and the broth from cell suspension culture were compared to those of mesquite gum and all three samples exhibited similar emulsifying capacity and emulsification stability.