Distilled jujube liquor is an alcoholic beverage made from jujube, which has a unique flavor and a sweet taste. The purpose of this study was to explore the effect of mixed fermentation on the quality of distilled jujube liquor by comparing the performance of mixed fermentation between S. cerevisiae, Pichia pastoris and Lactobacillus. The results showed that there were significant differences in the quality of the jujube liquor between the combined strains. Moreover, Lactobacillus increased and P. pastoris reduced the total acid content. The results from an E-nose showed that the contents of methyl, alcohol, aldehyde, and ketone substances in the test bottle decreased significantly after decanting, while the contents of inorganic sulfide and organic sulfide increased. Fifty flavor compounds were detected, including nineteen esters, twelve alcohols, seven ketones, six aldehydes, three alkenes, one furan, one pyridine, and one acid. There were no significant differences in the type or content of flavor compounds. However, PLS-DA showed differences among the samples. Eighteen volatile organic compounds with variable importance in projection values > 1 were obtained. There were sensory differences among the four samples. Compared with the sample fermented with only S. cerevisiae, the samples co-fermented with Lactobacillus or with P. pastoris had an obvious bitter taste and mellow taste, respectively. The sample fermented by all three strains had a prominent fruity flavor. Except for the sample fermented with only S. cerevisiae, the jujube flavor was weakened to varying degrees in all samples. Co-fermentation could be a valuable method to improve the flavor quality of distilled jujube liquor. This study revealed the effects of different mixed fermentation modes on the sensory flavor of distilled jujube liquor and provided a theoretical basis for the establishment of special mixed fermentation agents for distilled jujube liquor in the future.

Adsorbent material was prepared using distillers’ grains (DG), which is a waste product of distilleries. The DG was pre-treated with NaOH and esterification-modified with CS2, which is a commonly used anionic modifier. The structure and morphology of the adsorbent was characterized by FTIR, XRD, EDS, SEM, BET, and zeta potential. The related mechanism of adsorption of malachite green (MG) onto modified distiller’s grains (MDG) was studied by adsorption experiments and molecular simulation techniques. The experimental results showed that CS2 successfully modified the DG fiber, and simultaneously yielded the MDG with a uniform pore distribution. MDG had a considerable adsorption capacity of 367.39 mg/g and a maximum removal rate of 96.51%. After eight adsorption–desorption cycle experiments, the adsorption removal rate of MDG to MG dye remained at 82.6%. The adsorption process could be fitted well by a pseudo-second-order kinetic model (the correlation coefficient R2 > 0.998) and Freundlich isotherm adsorption equation (the correlation coefficient R2 > 0.972). Moreover, the adsorption of MG dye by MDG is a spontaneous, endothermic, and increased entropy process. The results of molecular simulation showed that the mechanism of MG molecules onto MDG was mainly chemical adsorption. The adsorption performance of MG onto MDG was better and more stable than DG. Molecular simulation also provided a theoretical guidance of MDG adsorption–desorption for the research on recycling of DG resources.

This study investigates innovative approaches to improve the quality and aroma characteristics of Muscat Hamburg wine production by substituting the conventional Saccharomyces cerevisiae yeast with an efficient fermentation strain of Schizosaccharomyces pombe. The typical use of S. cerevisiae in Muscat Hamburg wine often leads to uniformity and prolonged processing times, requiring subsequent malolactic fermentation to degrade excessive malic acid. The study advocates for the replacement of S. cerevisiae with a specific S. pombe strain, Sp-410, isolated from the fermented grains of sauce-flavor Baijiu, a Chinese spirit. Muscat Hamburg wine fermented with the S. pombe strain demonstrates decreased malic acid levels, offering a potential alternative to malolactic fermentation. However, exclusive S. pombe fermentation may result in an overproduction of acetic acid metabolites, leading to a monotonous taste. In response, the study proposes a mixed fermentation approach, combining the S. pombe strain with a Saccharomyces uvarum strain and a non-Saccharomyces yeast, Torulaspora delbrueckii. The optimized mixed fermentation strategies (M:SP+TD and M60SP+TD) involve specific proportions and intervals of inoculation, aiming to enhance the quality and aroma complexity of Muscat Hamburg wine. In conclusion, this research contributes to advancing the production of high-quality Muscat Hamburg wines, utilizing S. pombe as the primary yeast strain and implementing mixed fermentation methodologies.

Using distillers grains (DG) as raw material after pre-treatment with sodium hydroxide (NaOH) and modified with cationic etherification agent 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC), cationic quaternary ammonium distillers grains adsorption material (CDG) was successfully prepared. The optimal adsorption conditions were an adsorption temperature of 25 °C, adsorption time of 180 min, amount of adsorbent at 8.5 g/L, initial dye concentration of 100 mg/L, and pH of dye solution 7.0. The structure of CDG was characterized by FTIR, EDS, SEM, BET, ultraviolet spectrum analysis, and analysis of the zeta potential, while the adsorption mechanism was studied by adsorption kinetics, isotherms, and thermodynamics. The results showed that CHPTAC modified the distillers grains successfully and induced the formation of CDG with a large number of pore structures and good adsorption effect. The highest adsorption yield was above 98%, while after eight rounds of adsorption–desorption experiments, the adsorption rate was 81.80%. The adsorption mechanism showed that the adsorption process of acid yellow 11 (AY11) by CDG conforms to the pseudo-second-order kinetic model, mainly with chemical and physical adsorption such as pore adsorption and electrostatic adsorption. Thermodynamics conforms to the Freundlich isothermal model, and the adsorption process is a spontaneous, endothermic and entropy-increasing process.

In order to explore the effect of Wickerhamomyces on the production of flavor compounds in Xiaoqu Baijiu (XQBJ), this study examined the correlation between the fungal communities in Xiaoqu and ester compounds. It was hypothesized that Wickerhamomyces contributes to the aroma of Xiaoqu. Intensified fermentation methods were used to validate the role of Wickerhamomyces anomalus in XQBJ brewing. Compared to traditional Xiaoqu, intensified fermentation significantly increased the acidity of fermented grains and starch utilization rate (p < 0.05). The fungal communities in fermented grains were analyzed by high-throughput sequencing technology. The dominant fungi in both control and test groups were Saccharomyces, Cyberlindnera, Rhizopus, and Meyerozyma, with Wickerhamomyces replacing Saccharomymycopsis in the enhanced group. Flavor compounds in the fermentation experiments were analyzed, revealing that ethyl acetate content in XQBJ increased by 949.94 mg/L in the test group, while isoamyl alcohol decreased by 23.62 mg/L and isobutanol decreased by 34.81 mg/L. Functional prediction analysis using PICRUSt2 confirmed a higher relative abundance of enzymes involved in ethyl acetate metabolism and a lower relative abundance of enzymes involved in higher alcohol metabolism in the test group. These findings demonstrate that Wickerhamomyces enhances ethyl acetate production and reduces higher alcohols during XQBJ brewing, offering a theoretical foundation for enhancing the quality of XQBJ.

To explore microbial resources for ester production in sub-high-temperature Daqu, this study first established that the esterifying enzyme activity in Daqu predominantly originated from fungi, with Rhizopus being the dominant fungal genus. Six Rhizopus strains capable of decomposing esters were isolated and purified from Daqu. Following secondary screening, strain M1 exhibited the highest esterification activity (40.26 U/mL) and was identified as Rhizopus oryzae based on morphological characteristics and molecular biological analyses. This strain was subsequently designated as Rhizopus oryzae M1 (R. oryzae M1). Using mycelial powder of strain M1 as the inoculum and sterilized wheat bran as the substrate, a pure-culture Fuqu was prepared. Orthogonal array design experiments were conducted to optimize the preparation process of this Fuqu, using esterifying enzyme activity as the evaluation index. Under the optimal conditions, the spore count and esterification activity of the pure-culture Fuqu reached 1.73 × 10⁹ CFU/g and 80.13 U/g, respectively. This pure-culture Fuqu was subsequently used as an inoculum to produce fortified Daqu. Following orthogonal optimization of the Daqu preparation process, the esterification activity of the fortified Daqu reached 103.22 U/g, and its key physicochemical indices met the requirements for high-quality sub-high-temperature Daqu. Analysis of the microbial community structure revealed that Rhizopus was the dominant fungal genus in the fortified Daqu, with its relative abundance increased by 35% compared to the non-fortified Daqu. Consistent with this, the esterifying enzyme activity of the fortified Daqu was 51.79% higher, suggesting that Rhizopus may have been largely responsible for the increase in esterification capacity. In laboratory-scale Baijiu brewing trials, this fortified Daqu produced a base Baijiu with a total ester content of 2.74 g/L, representing a 40.5% increase over the non-fortified Daqu and further confirming the pivotal role of Rhizopus in driving the esterifying enzyme activity. This study successfully screened a high esterifying enzyme-producing strain, R. oryzae M1, systematically optimized its enzyme production and Qu-making processes, and provides an excellent microbial strain and process reference for the preparation of fortified Daqu and the enhancement of Baijiu flavor.