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

Fermentative performance of indigenous Lachancea thermotolerans in high-sugar and low-acid wine production: Insights from volatomics and metabolomics

The impact of climate change on grapevine cultivation has led to challenges in winemaking, particularly in terms of elevated sugar levels and reduced acidity in grapes. To address this, the specie of Lachancea thermotolerans (LT) with high lactic acid production potential have gained attention. This study explores the co-fermentation of the selected LT with Saccharomyces cerevisiae CECA to improve the chemical and flavor profiles of wine. Four different inoculation timings were tested in Cabernet Sauvignon fermentation to investigate the effects on metabolic pathways and fermentation performances. The results indicated that indigenous L. thermotolerans A38 slightly prolonged the fermentation time (13-14 days) but produced wine with lower volatile acidity compared to the pure inoculations of S. cerevisiae CECA (12 days). In contrast, co-fermentation with L. thermotolerans A38 led to the higher acidity and altered the metabolic profile of the wine, including increased lactic acid production (1.38-3.02 g/L), especially when S. cerevisiae was inoculated 48 h after LT fermentation (3.02 g/L). In co-fermented wines with LT strain, the levels of several aromatic volatiles, including phenylethyl alcohol (increasing by 4.10-37.64 %), phenylethyl acetate (by 6.72-302.19 %), ethyl lactate (by 4.48 folds), and ethyl acetate (by 2.65-83.07 %), were significantly increased, along with some terpenes. Metabolomics analysis revealed that different inoculation timings significantly influenced the microbial biosynthesis pathways of flavonoids and amino acids, thereby altering the production of aromatic compounds. This study provides new insights into the role of L. thermotolerans in winemaking and presents an effective strategy for addressing the acidity issues associated with climate change-induced grape composition changes.

Evolution During Bottle Ageing of Wines Macerated with Toasted Vine-Shoots and Micro-Oxygenation

The effects of SEGs ("Shoot from vines-Enological-Granule") on winemaking within the same variety are well established. However, the interaction of different SEG varieties combined with micro-oxygenation (MOX) and its subsequent evolution in the bottle has not been investigated to date. In this work, Tempranillo wines were treated with two doses of SEGs from Tempranillo and Cabernet Sauvignon (12 and 24 g/L) and subjected to two fixed MOX doses (LOTR, 6.24 mg/L·month, and HOTR, 11.91 mg/L·month). After that, the wines were bottled, and their chemical composition and sensory profile were analysed after 3 and 6 months. Although no clear trend directly associated with the use of MOX was observed, in terms of chemical composition, wines showed an evolution in their chemical profile over time, with compounds such as vanillin increasing as more oxygen was added. Regarding their sensorial profile, the wines were more rounded after 6 months that in bottling, where SEGs or toasted descriptors, studied at the taste phase, were slightly more intense with the low SEG dose and HOTR combination.

Metabolomics and HS-SPME-GC-MS-based analysis of quality succession patterns and flavor characteristics changes during the fermentation of Lycium barbarum and Polygonatum cyrtonema compound wine

This work set out to investigate how the physicochemical markers, volatiles, and metabolomic characteristics of mixed fermented the fermentation of Lycium barbarum and Polygonatum cyrtonema compound wine (LPCW) from S. cerevisine RW and D. hansenii AS2.45 changed over the course of fermentation. HS-SPME-GC-MS combined with non-targeted metabolomics was used to follow up and monitor the fermentation process of LPCW. In total, 43 volatile chemical substances, mostly alcohols, esters, acids, carbonyl compounds, etc., were discovered in LPCW. After 30 days of fermentation, phenylethyl alcohol had increased to 3045.83 g/mL, giving off a rose-like fresh scent. The biosynthesis of valine, leucine, and isoleucine as well as the metabolism of alanine, aspartic acid, and glutamic acid were the major routes that led to the identification of 1385 non-volatile components in total. This study offers a theoretical foundation for industrial development and advances our knowledge of the fundamental mechanism underlying flavor generation during LPCW fermentation.

Effects of down-regulation of ackA expression by CRISPR-dCpf1 on succinic acid production in Actinobacillus succinogenes

Succinic acid (SA), a key intermediate in the cellular tricarboxylic acid cycle (TCA), is a 4-carbon dicarboxylic acid of great industrial value. Actinobacillus succinogenes can ferment various carbon sources and accumulate relatively high concentrations of SA, but few reliable genetic engineering tools exist for A. succinogenes and this has hindered strain improvement to increase SA production for industrial application. Two different repressors, endonuclease-deactivated Cas9 (dCas9) from Streptococcus pyogenes and Cpf1 (dCpf1) from Francisella tularensis, were applied to construct a CRISPRi system in A. succinogenes. Codon-optimized Cas9 and native Cpf1 were successfully expressed in A. succinogenes, and the corresponding sgRNA and crRNA expression elements, promoted by the fumarate reductase promoter, frd, were introduced into the CRISPRi plasmid. The highest repression of the ackA gene (encoding acetate kinase) and thereby acetic acid production (~ eightfold) was achieved by the dCpf1-based CRISPRi system, in which the mutation site, E1006A acted at the start of the coding region of ackA, the gene which regulates acetic acid biosynthesis. Compared with the ackA gene knockout mutant, cell growth was moderately improved and SA production increased by 6.3%. Further, the SA titer and productivity in a 3 L fermenter reached 57.06 g/L and 1.87 g/L/h, and there was less acetic acid production. A dCpf1-based CRISPRi-mediated gene repression system was successfully established for the first time, providing a simple and effective tool for studying functional genomics in A. succinogenes and optimizing SA production.

Cell Immobilization for Erythritol Production

Nowadays, commercial erythritol synthesis is performed by free-cell fermentation with fungi in liquid media containing high concentrations of pure carbon sources. Alternative fermentation techniques, such as cell immobilization, could imply an economic and energetic improvement for erythritol-producing factories. The present work describes, for the first time, the feasibility of achieving cell immobilization during erythritol production. Cells of the fungus Moniliella pollinis were successfully immobilized on a cotton cloth which was placed inside a 2-L bioreactor, where they were fed with red grape must supplemented with yeast extract. They produced 47.03 ± 6.16 g/L erythritol in 96 h (yield 0.18 ± 0.04 g/g) over four consecutive fermentation batches. The immobilized cells remained stable and operative during a 456 h period. The erythritol concentration attained was similar (p > 0.05; Tukey HSD test) to the reference value obtained with the use of free cells (41.88 ± 5.18 g/L erythritol) under the same fermentation conditions. The comparable results observed for free and immobilized cells evidences the efficiency of the immobilization system. Therefore, the proposed method for erythritol bioproduction eliminates the need for the continuous preparation of fungal inocula before each fermentation batch, thus reducing the costs of the reagents and energy.