Revisiting the production of L( +)-lactic acid from vine shoots: bioconversion improvements by employing thermotolerant bacteria

Abstract

Vine shoots (Vitis vinifera L.) constitute an abundant lignocellulosic source which is frequently underutilised. Alkaline and acidic pretreatments (with and without washing steps) were compared and optimised to release fermentable sugars from vine shoots. An acidic pretreatment using 1.72% H 2 SO 4 at 134 °C for 17 min (with 10% w/w solid biomass), followed by an enzymatic hydrolysis, offered the most cost-effective results, releasing 40.21 g/L sugars. Three thermotolerant strains, namely, Bacillus coagulans DSM 2314, Geobacillus stearothermophilus DSM 2313, and G. stearothermophilus DSM 494, were assessed to produce lactic acid from vine-shoot hydrolysates under aerobic and non-sterile conditions, without the need of detoxification steps. In addition, wine lees were satisfactorily employed as nitrogen sources for the fermentation, providing similar results to yeast extract and being the only nutrient added to vine-shoot hydrolysates. Under optimal conditions, B. coagulans DSM 2314 produced 29.21 ± 0.23 g/L lactic acid in 24 h, with a sugar consumption of 98.74 ± 0.07% and a yield of 96.38 ± 0.76%, when supplemented with red wine lees. The purity of the isomer L( +) reached 97.59 ± 1.35% of the total lactic acid produced. Although G. stearothermophilus was able to transform the hexoses from vine-shoot hydrolysates into lactic acid, it proved to be inefficient for metabolising pentoses, thus obtaining lower lactic acid values (16-18 g/L). Key points • Thermotolerant bacteria produced L( +)-lactic acid from vine shoots• Bacillus coagulans obtained a yield of 96% lactic acid from vine-shoot hydrolysates • Lactic acid can be produced with wine lees as the only additional nitrogen source

Current Options in the Valorisation of Vine Pruning Residue for the Production of Biofuels, Biopolymers, Antioxidants, and Bio-Composites following the Concept of Biorefinery: A Review

“…Chemical pre-treatment consists of using different catalysts, such as acids, alkali, and oxidizing agents. The most widely used acid for the fractionation of lignocellulosic materials is H 2 SO 4 [46]. It converts hemicelluloses into simpler sugars.…”

“…In another study, Garita-Cambronero and co-workers [46] applied alkaline and acid pretreatments (with and without washing steps) to obtain VPR sugars. The best results were obtained for the recovery of sugars (40.21 g/L) when using acid pre-treatment with 1.7% H 2 SO 4 , 134 • C for 17 min with 10% w/w VPR, followed by enzymatic hydrolysis.…”

Assessment of vine shoots and surplus grape must for succinic acid bioproduction

“…Dry vine shoots contained 32.77% glucan, 11.31% hemicellulose (49.27% total carbohydrates), 2.82% galacturonic acid, 21.30% acid-insoluble lignin, 4.34% protein, 0.52% fat, 7.91% moisture, 2.40% ashes and 13.3 mg/g total phenolic compounds. In order to release the sugars contained in vine shoots, they were subjected to an acidic hydrolysis with 1.72% H2SO4 (w/w) at 134 °C for 17 min, with 10% (w/w) solids; followed by an enzymatic hydrolysis for 48 h at 50 °C, 150 rpm and pH 5.0, with the enzyme mixture Cellic CTec2 (Novozymes, Bagsvaerd, Denmark) at a dose of 17.4 FPU per 1 g biomass, as described by Garita-Cambronero et al [16]. Then, vine-shoot hydrolysates were vacuum-filtered (filter paper No.…”

Multi-feedstock biorefinery concept: Valorization of winery wastes by engineered yeast

“…Vine shoots (VS) from the agronomic practice of pruning account for up to 93% of winery leftovers (Sánchez et al, 2002). VS are composed of cellulose, hemicellulose, and lignin and can be considered as a platform synthesis of a plethora of biobased products such as oligosaccharides, proteins, lactic acid, bioactive compounds, biosurfactants, xylitol, and biofuels such as ethanol and biogas (Cortés-Camargo et al, 2016;Dávila et al, 2016;Garita-Cambronero et al, 2021;Jesus et al, 2017Jesus et al, , 2019Pachón et al, 2020;Pérez-Rodríguez et al, 2016;Rajha et al, 2014;Rivas et al, 2007). In this sense, using VS as a source of energy and value-added products rather than combusting or disposing on the ground to decompose is a more cost-effective and environmentally friendly option.…”