Sugars metabolism and ethanol production by different yeast strains from coffee industry wastes hydrolysates

Significant amounts of wastes are generated by the coffee industry, among of which, coffee silverskin (CS) and spent coffee grounds (SCG) are the most abundantly generated during the beans roasting and instant coffee preparation, respectively. This study evaluated the sugars metabolism and production of ethanol by three different yeast strains (Saccharomyces cerevisiae, Pichia stipitis and Kluyveromyces fragilis) when cultivated in sugar rich hydrolysates produced by acid hydrolysis of CS and SCG. S. cerevisiae provided the best ethanol production from SCG hydrolysate (11.7 g/l, 50.2% efficiency). On the other hand, insignificant (<= 1.0 g/l) ethanol production was obtained from CS hydrolysate, for all the evaluated yeast strains, probably due to the low sugars concentration present in this medium (approx. 22 g/l). It was concluded that it is possible to reuse SCG as raw material for ethanol production, which is of great interest for the production of this biofuel, as well as to add value to this agro-industrial waste. CS hydrolysate, in the way that is produced, was not a suitable fermentation medium for ethanol production; however, the hydrolysate concentration for the sugars content increase previous the use as fermentation medium could be an alternative to overcome this problem. (C) 2011 Elsevier Ltd. All rights reserved.

Medium Light and Medium Roast Paper-Filtered Coffee Increased Antioxidant Capacity in Healthy Volunteers: Results of a Randomized Trial

We compared the effects of medium light roast (MLR) and medium roast (MR) paper-filtered coffee on antioxidant capacity and lipid peroxidation in healthy volunteers. In a randomized crossover study, 20 volunteers consumed 482 +/- 61 ml/day of MLR or MR for four weeks. Plasma total antioxidant status (TAS), oxygen radical absorbance capacity (ORAC), oxidized LDL and 8-epi-prostaglandin F2 alpha, erythrocyte superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) activity were measured at baseline and after the interventions. MLR had higher chlorogenic acids-(CGA; 334 mg/150 mL) and less caffeine (231 mg/150 ml) than MR had (210 and 244 mg/150 ml, respectively). MLR also had fewer Maillard reaction products (MRP) than MR had. Compared with baseline, subjects had an increase of 21 and 26 % in TAS, 13 and 13 % in CAT, 52 and 75 % in SOD, and 62 and 49 % in GPx after MLR and MR consumption (P < 0.001), respectively. ORAC increased after MLR (P = 0.004). No significant alteration in lipid peroxidation biomarkers was observed. Both coffees had antioxidant effects. Although MLR contained more CGA, there were similar antioxidant effects between the treatments. MRP may have contributed as an antioxidant. These effects may be important in protecting biological systems and reducing the risk of diseases related to oxidative stress.