Inside the guts of wood-eating catfishes: can they digest wood?

To better understand the structure and function of the gastrointestinal (GI) tracts of wood-eating catfishes, the gross morphology, length, and microvilli surface area (MVSA) of the intestines of wild-caught Panaque nocturnus, P. cf. nigrolineatus “Marañon”, and Hypostomus pyrineusi were measured, and contrasted against these same metrics of a closely related detritivore, Pterygoplichthys disjunctivus. All four species had anatomically unspecialized intestines with no kinks, valves, or ceca of any kind. The wood-eating catfishes had body size-corrected intestinal lengths that were 35% shorter than the detritivore. The MVSA of all four species decreased distally in the intestine, indicating that nutrient absorption preferentially takes place in the proximal and mid-intestine, consistent with digestive enzyme activity and luminal carbohydrate profiles for these same species. Wild-caught Pt. disjunctivus, and P. nigrolineatus obtained via the aquarium trade, poorly digested wood cellulose (<33% digestibility) in laboratory feeding trials, lost weight when consuming wood, and passed stained wood through their digestive tracts in less than 4 h. Furthermore, no selective retention of small particles was observed in either species in any region of the gut. Collectively, these results corroborate digestive enzyme activity profiles and gastrointestinal fermentation levels in the fishes’ GI tracts, suggesting that the wood-eating catfishes are not true xylivores such as beavers and termites, but rather, are detritivores like so many other fishes from the family Loricariidae

Production of grape pomace extracts with enhanced antioxidant and prebiotic activities through solid-state fermentation by Aspergillus niger and Aspergillus oryzae

Grape pomace is a winery by-product that accumulates in high amounts in winemaking industry, which usually found difficulties regarding its disposal. Nonetheless, it has a great proportion of polyphenols which can be recovered to valorise this biomass. Filamentous fungi produce hydrolytic enzymes, which can assist in the liberation of polyphenols. Grape pomace was fermented in solid-state by Aspergillus niger and Aspergillus oryzae with the aim of facilitating the aqueous extraction of polyphenols with antioxidant activity by on-site enzyme production. Both fungi increased the antioxidant activity of the extracts, reaching maximum values of 73.7 ± 0.8 (A. niger) and 109.2 ± 0.5 (A. oryzae) mmol of Trolox equivalents/100 g of grape pomace. During fermentations, relevant enzymes were produced at high yields, A. niger produced a balanced profile of enzymes (cellulase, tannase, and pectinase), while A. oryzae switches to cellulase or tannase selective induction according to the fermentation conditions. Positive correlations were found between enzyme production, polyphenols recovery, and antioxidant activity. The extracts obtained after fermentation promoted the growth of Lactobacillus casei cultures. Therefore, the solid-state fermentation was effective for the simultaneous production of relevant industrial enzymes and grape pomace extracts with antioxidant and prebiotic properties, which have potential as functional food additives.Fil: Meini, María Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Químicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Procesos Biotecnológicos y Químicos Rosario; ArgentinaFil: Cabezudo, Ignacio. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Galetto, Cecilia Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Químicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Procesos Biotecnológicos y Químicos Rosario; ArgentinaFil: Romanini, Diana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Químicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Procesos Biotecnológicos y Químicos Rosario; Argentin