Bioconversion of Vitis vinifera L. (CV. Merlot and CV. Sauvignon Blanc) Grape Residues by Hermetia illucens

This study investigated the bioconversion of winemaking residues from Vitis vinifera L. grapes (Merlot and Sauvignon Blanc) using larvae of Hermetia illucens (Black Soldier Fly - BSF). Preliminary tests showed that pure grape pomace did not support larval development, necessitating supplementation of diets with a farinaceous residue composed of 97% wholemeal flour and 3% yeast. Six treatments were established, varying the proportions of grape pomace and farinaceous residue: MG1 (25% Merlot, 75% farinaceous), MG2 (50% Merlot, 50% farinaceous), MG3 (75% Merlot, 25% farinaceous), SBG1 (25% Sauvignon Blanc, 75% farinaceous), SBG2 (50% Sauvignon Blanc, 50% farinaceous), and SBG3 (75% Sauvignon Blanc, 25% farinaceous). The results indicated that Sauvignon Blanc pomace was more efficient in bioconversion, with the SBG75 treatment achieving the highest biomass gain (888.9 ± 43.16%) and the best bioconversion efficiency (29.63 ± 1.43%). Merlot pomace, particularly the MG75 treatment, showed lower biomass gain (693.1 ± 38.8%) and efficiency (23.10 ± 1.29%). However, the MG50 treatment, with 50% Merlot pomace, achieved the highest conversion rate (2.70 ± 0.31 g/g/day). These findings suggest that Sauvignon Blanc pomace is more effective in promoting larval growth and waste conversion, possibly due to differences in nutritional composition and digestibility compared to Merlot pomace. While Merlot pomace demonstrated positive performance, Sauvignon Blanc pomace proved superior in terms of larval development and bioconversion efficiency.