Grape stalk valorization for fermentation purposes.

White and red grape stalks biomass were fractioned to maximize its economic value by the production of fermentable sugars, as other value streams. High yields of extractives and lignin were first obtained, originating a biomass rich in cellulose and hemicellulose, which was subject to acid and enzymatic hydrolysis for production of fermentable sugars. Higher concentrations of sugars were obtained by enzymatic than by dilute acid hydrolysis. These biosugars were used for fermentation processes with Pichia stipitis and Saccharomyces cerevisiae. The presence of higher quantities of xylose favoured P. stipitis to produce higher ethanol yields than S. cerevisiae which is glucose lover. Cellulose nanocrystals were produced from the resulting biomass without monosaccharides. For the first time an integrated valorization of grape stalks followed by an application of one of the valorized streams is presented.

In vitro ACE-inhibitory peptide KGYGGVSLPEW facilitates noradrenaline release from sympathetic nerve terminals: Relationship with the lack of antihypertensive effect on spontaneous hypertensive rats.

This study aimed to validate the antihypertensive activity of the angiotensin-converting enzyme (ACE)-inhibitor whey protein hydrolysate (WPH) obtained through the action of proteolytic enzymes from Cynara Cardunculus. The antihypertensive activity of WPH fractions containing peptides with molecular weight below 3kDa (Whey<3kDa) and 1kDa (Whey<1kDa) along with the antihypertensive activity of three potent ACE-inhibitory peptide sequences (DKVGINYW, DAQSAPLRVY and KGYGGVSLPEW), previously identified in WPH, were also investigated. In parallel, the influence of KGYGGVSLPEW (the most potent ACE-inhibitory peptide sequence) on AT1 receptors (a common pharmacological target of antihypertensive therapies beyond ACE), was evaluated. The effect of WPH and fractions (300mg/kg) and peptide sequences (5mg/kg) on systolic, diastolic and mean blood pressure was evaluated by telemetry on spontaneously hypertensive rats (SHR), after single oral administration. Despite their ACE-inhibitory effect in vitro, neither WPH, Whey <3kDa, Whey <1kDa or peptide sequences exhibited antihypertensive activity. In addition, KGYGGVSLPEW was not only devoid of AT1 receptor antagonism but, on the contrary, had a similar effect to that of Ang II by facilitating the noradrenaline release from sympathetic nerve terminals. In vitro ACE blockade does not always correlate with antihypertensive activity and food-derived peptides cannot be classified as antihypertensive agents based exclusively on in vitro assays. The absence of an antihypertensive effect may also be a result of the interaction of these compounds with other components of the systems involved in the blood pressure control.

Bioactive peptides: are there more antihypertensive mechanisms beyond ACE inhibition?

Diet has a high relevance in health. Hypertension is a major risk factor for cardiovascular diseases and has an important impact on public health, and consequently on countries economy. Scientific research gathered strong evidence about the role of several dietary factors either in etiology or in treatment/prevention of these diseases. Peptides from different food matrices have been studied, and indicated as compounds with particular interest in the context of hypertension. The classical approach involves the identification of peptides with an in vitro ACE inhibitory activity and the assumption that the observed in vivo effects are due to this enzyme blockade. However, in some cases the potency of ACE blockade does not correlate with the antihypertensive activity in vivo. This paper reviews the current literature that identifies mechanisms of action, other than ACE inhibition, that might explain antihypertensive effects of biologically active peptides from different food sources.