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The present study was aimed at assessing the biotransformation of dark fermented agroindustrial residues and energy crops for the production of hydrogen and poly-β-hydroxybutyrate (PHB), in lab-scale photofermentation. The investigation on novel substrates for photofermentation is needed in order to enlarge the range of sustainable feedstocks. Dark fermentation effluents of ensiled maize, ensiled giant reed, ensiled olive pomace, and wheat bran were inoculated with Rhodopseudomonas palustris CGA676, a mutant strain suitable for hydrogen production in ammonium-rich media. The highest hydrogen producing performances were observed in wheat bran and maize effluents (648.6 and 320.3 mL L −1 , respectively), both characterized by high initial volatile fatty acids (VFAs) concentrations. Giant reed and olive pomace effluents led to poor hydrogen production due to low initial VFAs concentrations, as the original substrates are rich in fiber. The highest PHB content was accumulated in olive pomace effluent (11.53%TS), ascribable to magnesium deficiency. [ABSTRACT FROM AUTHOR]

The kinetic behaviour of olive tree pruning (PR), two- (2PH) and three-phase (3PH) olive pomace and their blends was investigated under combustion condition using thermogravimetric analysis. PR was blended with 2PH and 3PH at different ratios (25:75, 50:50 and 75:25) and tested in the temperature range from ambient to 1000 °C in order to evaluate the co-combustion behaviour. Results showed that the thermal degradation of all samples can be divided into three regions (drying, devolatilisation, char oxidation) with different combustion properties, depending on the percentage of PR. Significant interaction was detected between the fuels, and reactivity of 2PH and 3PH was improved upon blending with PR. The iso-conversional methods, Ozawa–Flynn–Wall and Vyazovkin, were employed for the kinetic analysis of the oxidation process. The results revealed that the activation energy of PR was higher than the one of 2PH and 3PH, and the minimum value was obtained for 25PR752PH sample. [ABSTRACT FROM AUTHOR]

Olive mills generate a large amount of waste that can be revaluated. This work aim to improve the production lignocellulolytic enzymes by solid-state fermentation using ultrasounds pretreated olive mill wastes. The composition of olive mill wastes (crude and exhausted olive pomace) was compared and several physicochemical characteristics were significantly different. The use of both wastes in SSF was evaluated and a screening of fungi for xylanase and cellulase production was carried out. After screening, the use of exhausted olive pomace and Aspergillus niger led to the highest enzyme activities, so that they were used in the study of ultrasounds pre-treatment. The results showed that the sonication led to a 3-fold increase of xylanase activity and a decrease of cellulase activity. Moreover, the liquid fraction obtained from ultrasounds treatment was used to adjust the moisture of solid and a positive effect on xylanase (3.6-fold increase) and cellulase (1.2-fold increase) production was obtained. [ABSTRACT FROM AUTHOR]

Aim of this study was to evaluate the suitability of ensiled giant reed, ensiled maize, ensiled olive pomace, wheat bran for combined systems (CS: dark fermentation + anaerobic digestion (AD)) producing hydrogen-rich biogas (biohythane), tested in batch under basic operational conditions (mesophilic temperatures, no pH control). Substrates were also analyzed under a single stage AD batch test, in order to investigate the effects of DF on estimated energy recovery (ER) in combined systems. In CS, maize and wheat bran exhibited the highest hydrogen potential (13.8 and 18.9 NL kgVS −1 ) and wheat bran the highest methane potential (243.5 NL kgVS −1 ). In one-stage AD, giant reed, maize and wheat bran showed the highest methane production (239.5, 267.3 and 260.0 NL kgVS −1 ). Butyrate/acetate ratio properly described the dark fermentation, correlating with hydrogen production ( r = 0.92). Wheat bran proved to be a promising residue for CS in terms of hydrogen/methane potential and ER. [ABSTRACT FROM AUTHOR]

Abstract: Polyhydroxyalkanoate (PHA) was produced in bench-scale sequencing batch reactors (SBRs) fed olive pomace fermentate containing a mixed microbial consortium. Initial anaerobic fermentation in a sequencing batch fermentor (SBF) produced soluble carbon compounds, mainly organic acids. SBF effluent was centrifuged, removing solids, and fed into a SBR where intracellular PHA was produced. Buffer pre-treatment of diluted olive pomace increased organic acid production 75% in SBF fermentate over no pre-treatment. Hydraulic retention time (HRT), solids retention time (SRT), pomace concentration/dilution, and aerobic operation vs. anoxic/oxic cycling were studied to improve PHA formation. Maximum %PHA achieved was 39% (on a dry-weight cell basis), and the highest volumetric productivity was 0.042g PHA/L-day under fully aerobic conditions. The highest PHA conversion yield was 0.3625g PHA/L fermentate. [Copyright &y& Elsevier]

Abstract: Speciation of Cr(III)/Cr(VI) from water using olive pomace (OP) was improved by partial pyrolysis of OP. The sorbents were characterized by physicochemical techniques. Sorption of Cr(III) on raw and partially pyrolyzed OP sorbents followed Freundlich isotherm and second-order rate kinetics. OP pyrolyzed at 150°C (sorbent OP-150) exhibited maximum sorption capacity, favorability and the lowest sorption energy. Sorption was exothermic and spontaneous for the raw-OP and OP pyrolyzed at 100 or 150°C; but endothermic and non-spontaneous for OP pyrolyzed at 200, 250, 300 or 400°C. A speciation method of chromium was proposed, in which Cr(III) was selectively retained at pH 3 on sorbent OP-150; while total Cr was determined after reduction of Cr(VI). The method was selective with a detection limit for Cr(III) of 1.58μgL−1. The method was applied on natural and industrial waters (recoveries >97.7%, RSD’s <9%) and on tobacco leaves certified reference material (INCT-PVTL-6). [Copyright &y& Elsevier]

Abstract: In the present work, microbial lipase from Thermomyces lanuginosus was immobilized by covalent binding onto olive pomace. Immobilized support material used to produce biodiesel with pomace oil and methanol. The properties of the support and immobilized derivative were evaluated by scanning electron microscopy (SEM). The maximum immobilization of T. lanuginosus was obtained as 18.67mg/g support and the highest specific activity was 10.31U/mg protein. The properties of immobilized lipase were studied. The effects of protein concentration, pH and buffer concentration on the immobilization and lipase activity were investigated. Biodiesel production using the immobilized lipase was realized by a three-step addition of methanol to avoid strong substrate inhibition. Under the optimized conditions, the maximum biodiesel yield was 93% at 25°C in 24h reaction. The immobilized enzyme retained its activity during the 10 repeated batch reactions. [ABSTRACT FROM AUTHOR]

Abstract: Olive pomace was composted by using a reactor for a period of 50days in four bioreactors. Urea was added to adjust C/N ration between 25–30. At the end of 50days of composting using Trichoderma harzianum and Phanerochaete chrysosporium, cellulose and lignin were highly degraded. It was found that after 30days, P. chrysosporium and T. harzianum degraded approximately 71.9% of the lignin and 59.25% of the cellulose, respectively. The percent of ash content in the raw waste mixture was 13%. This percentage increased from 13% to 18.55% in treatment bioreactors and from 13% to 13.55% in control reactors during 50day of composting process. The amount of CO2 produced by the treated sample was 3mg of CO2/g organic carbon which is indicated that the treated sample was considered as stable compost. The results proved that the use of accelerating agents was found to be efficient in producing mature stable with nearly non-phytotoxicity compared to control sample in less than 50days. [Copyright &y& Elsevier]

• Olive pomace and stones have high lignin and moderate polysaccharides contents. • Autohydrolysis was selective towards hemicelluloses producing xylo-oligosaccharides. • Cellulose and lignin were not affected by autohydrolysis. • Enzymatic glucan conversion was over 80% in 5 h and 30% (w/v) pomace or stones. Spent olive pomace from the two-phase extraction system of virgin olive oil and olive pomace oil, is a major agro-industrial residue. Present study aimed at the valorization of residual olive pomace and stones (seeds) by hydrothermal treatment and enzymatic hydrolysis of glucans. Both residues contain lignin (31.2% and 42.1%), glucans (13.8% and 15.3%) and xylans (18.9% and 20.3%). After hydrothermal pretreatment (130 °C, 30 min; severity factor log R 0 = 2.99), 65% and 75% of hemicelluloses (65% of xylan) were hydrolysed into xylo-oligosaccharides in pomace and stones, respectively. Cellulose and lignin were not substantially affected. Three commercial enzyme preparations, Saczyme Yield, Ultimase BWL 40 and Celluclast 1.5 L, were evaluated for saccharification of pomace or stones at three biomass loads (10, 20 and 30%, w/v). Saczyme and Ultimase were active with high solid loads (30%), reaching 80 and 90% of glucan conversion in pomace, and 40 and 55% in stones, respectively, after 5 h. [ABSTRACT FROM AUTHOR]