Sour beer production: impact of pitching sequence of yeast and lactic acid bacteria

Lactic acid bacteria have long been used in brewing to acidify mash or wort and in the production of traditional sour beer styles (Lambic, Gueuze) using spontaneous fermentation. This approach is time consuming (some sour beers are matured for three years to obtain the appropriate flavour), so many brewers choose a faster approach using mixed cultures (yeast and bacteria). In this study, the influence of the pitching sequence of bacteria and yeast on the fermentation process was evaluated (by rate of fermentation and acidification, attenuation degree and ethanol concentration). The trials were performed using three procedures: (i) the addition of bacteria followed by the yeast; (ii) the addition of the yeast followed by the bacteria and (iii) the simultaneous addition of yeast and bacteria. In each trial the following time intervals were applied: 24, 48 and 72 h. Weight loss of samples and drop in pH were measured daily, and ethanol content, real extract and lactic acid concentration measured at the end of the process. It was shown that the order of addition of yeast and bacteria determines the success of the lactic acid fermentation. The appropriate yield of lactic acid (ca. 6 g/L) and the drop in pH (<3.6) can be achieved by inoculating the bacteria prior to the inoculation of yeast. When yeast was pitched before the bacteria, the lactic acid content was ca. 2 g/L and pH was 3.9–4.2. © 2019 The Institute of Brewing & Distilling     

乳酸菌与酵母菌对牦牛酸乳品质形成的影响

为明确乳酸菌和酵母菌在牦牛酸乳品质形成中发挥的作用,以牦牛乳粉为原料、牦牛酸乳为发酵剂发酵酸乳,在发酵过程中分别抑制乳酸菌和酵母菌的活性,测定并比较正常发酵、抑制乳酸菌发酵、抑制酵母菌发酵酸乳的风味、口感、质构等相关指标。结果表明,乳酸菌和酵母菌对牦牛酸乳品质形成均起到关键作用,乳酸菌对酸乳酸度、质构、氨基酸态氮、有机酸、V_(B1)及酮类和酸类风味物质的贡献较大,酵母菌对乙醇、V_(B2)及醇类和酯类风味物质的贡献较大。     

Selection and modification of yeasts and lactic acid bacteria for wine fermentation

Historically, the fermentation of grape juice to wine has been carried out by indigenous yeasts found on the berry. However, in newer wine regions, e.g. the USA, inoculation with selected wine yeast strains is employed. Grape juice is high in nutritional factors and difficulties in fermentation usually arise from the inhibitory effects of the high concentration of sugar initially present and the ethanol produced. A secondary fermentation, brought about by indigenous or added lactic acid bacteria, converts malic acid to lactic acid and carbon dioxide and often occurs. This ‘malolactic’ fermentation is usually slow. For both yeast and bacterial fermentations strain selection is based more on fermentation performance than on sensory characteristics of the wine, with increased tolerance of the yeast to ethanol and of the bacteria to low pH being emphasized. Attempts to increase the malolactic fermentation rate have been made by cloning and transferring the malolactic gene from Lactobacillus to wine yeast. In early attempts to produce wines with enhanced or novel sensory characteristics a leucine-less mutant of a homothallic wine yeast has been obtained which does not produce isoamyl alcohol.     

奶啤生产中乳酸菌对酵母菌发酵作用的研究

利用乳酸菌和酵母菌的共生作用,对牛乳进行了混合菌种的发酵研究。分析了共生作用对产品pH值、滴定酸度、乙醇含量和α-氨基酸态氮的影响。研究结果表明,乳酸菌的加入不仅可以提高酵母菌的生长速度,而且可以提高产品的风味,奶啤的酒精含量相对啤酒较低,是酒精度较低的健康型饮料。     

直接乳酸发酵工艺研究进展

对以淀粉质为原料进行直接乳酸发酵的国内外研究现状进行了综述.介绍了利用米根霉等真菌和解淀粉乳酸细菌进行直接乳酸发酵.以及通过添加降解酶进行同步糖化发酵的三种直接乳酸发酵工艺.指出通过筛选和构建更加高效的具有解淀粉活性的乳酸细菌和真菌,同时通过获得耐受更高温度的乳酸菌来提高同步糖化发酵的温度,进而使直接乳酸发酵工艺更加高效.     

乳酸菌和酵母菌共酵改善食醋品质的研究

以黄河大米为原料进行乳酸菌和酵母菌的共生发酵,在单因素试验的基础上,采用正交试验探讨了乳酸菌、酵母菌的接种量、发酵时间及发酵温度对食醋的酒精度和乳酸含量的影响,并对其发酵工艺条件进行了优化。结果表明,当酵母菌接种量为1.0‰、乳酸菌接种量为5%、发酵温度为30 ℃、发酵时间为72 h时,发酵所得的酒醪中酒精度为7.8%vol,乳酸含量为0.54 g/100 mL。用该酒醪经液态深层法酿造的食醋中不挥发酸和酯类含量较优化前分别提高了10.25倍和1.62倍,并最终改善液醋的感官品质。     

利用一株凝结芽孢杆菌发酵酸解玉米秸秆生产乳酸

该研究拟考察凝结芽孢杆菌（Bacillus coagulans）利用玉米秸秆生物炼制乳酸的效果。以凝结芽孢杆菌CGMCC No.7635为菌种,利用2%硫酸预处理后的玉米秸秆为碳源、20 g/L酵母粉为氮源,添加20 FPU/g纤维素酶后开展糖化发酵生产乳酸实验。结果表明,发酵65 h后可获得乳酸含量为（38.38±1.03） g/L,其中L-乳酸光学纯度为（99.23±0.22）%。进一步使用补料发酵工艺,添加经预处理的玉米秸秆,可最终获得乳酸含量为（82.56±1.28） g/L。建立的玉米秸秆生物炼制乳酸工艺操作简单、产物浓度高,具有工业应用潜力。     

Rhizopus oryzae LS1利用丢糟水解液发酵生产乳酸

研究了一株诱变米根霉Rhizopus oryzae LS-1利用丢糟水解液发酵生产乳酸的可行性。首先考察R.oryzae LS-1利用葡萄糖和木糖的糖代谢差异特性,并通过正交实验优化丢糟水解液发酵生产乳酸的工艺参数。结果表明,R.oryzae LS-1能代谢利用葡萄糖和木糖,且二者存在协同互补作用,有利于乳酸生成和糖酸转化,可用于木质纤维原料的乳酸生产。丢糟水解液发酵生产乳酸的实验表明,氯化铵是R.oryzae LS-1适宜的氮源。在接种量为3.0%、p H为6.5、发酵时间为96h、Ca CO3添加量为80g/L的条件下,乳酸生成浓度为13.27g/L,糖利用率为79.61%。说明诱变菌株R.oryzae LS-1具备发酵丢糟水解液制备乳酸的潜力。      

传统发酵蔬菜中耐乙醇型乳酸菌的研究进展

发酵蔬菜一般都是由乳酸菌等多种微生物发酵而成,发酵过程中会产生有机酸、乙醇、氨基酸等物质。乙醇和有机酸形成酯类物质,赋予发酵蔬菜特有的香气。但是发酵蔬菜发酵过程中如果乙醇浓度过高,则会抑制乳酸菌发挥作用。因此,该文主要总结传统发酵蔬菜中乳酸菌的筛选方法、乳酸菌培养基优化、乳酸菌的乙醇耐受性、乳酸菌的诱变、乳酸菌的复配及应用等方面的研究进展,为人工接种乳酸菌发酵传统蔬菜产业化生产提供依据。     

机械化生产加饭酒发酵过程生物化学成份变化研究

对机械化生产加饭酒发酵过程中微生物变化规律进行了研究;通过对酵母菌总数、酵母形态、细菌总数、细菌形态、还原糖、总酸、挥发酸、酒精度、pH等生化指标的定期观察、检测研究及部分微量成份的定期测定研究,并对细菌进行初步检测和鉴定,乳酸杆菌是机械化生产加饭酒醪细菌类中的优势菌群;结果表明：机械化生产加饭酒的发酵过程是糖化与多品种、高密度酵母和乳酸杆菌（细菌）发酵协同作用的混合发酵并行的过程[即：边糖化与边酵母发酵、边乳酸杆菌（细菌）发酵同时协同进行的三边发酵];发酵过程高级醇和乳酸乙酯是逐渐增加的。     

Fermentation of beet juice by beneficial lactic acid bacteria

Red beets were evaluated as a potential substrate for the production of probiotic beet juice by four species of lactic acid bacteria (Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus delbrueckii, Lactobacillus plantarum). All the lactic cultures were found capable of rapidly utilizing beet juice for cell synthesis and lactic acid production. However, L. acidophilus and L. plantarum produced a greater amount of lactic acid than other cultures and reduced the pH of fermented beet juice from an initial value of 6.3 to below 4.5 after 48 h of fermentation at 30°C. Although the lactic cultures in fermented beet juice gradually lost their viability during cold storage, the viable cell counts of these lactic acid bacteria except for L. acidophilus in the fermented beet juice still remained at 10⁶–10⁸ CFU/ml after 4 weeks of cold storage at 4°C.     

Production of lactic acid from xylose and wheat straw by Rhizopus oryzae

Rhizopus oryzae NBRC 5378 was the best among 56 strains of R. oryzae for the production of lactic acid from xylose. This strain produced lactic acid from wheat straw powder by a simultaneous saccharification and fermentation process, with a yield of 0.23 g/g from cellulose and hemicellulose in wheat straw.     

清香型白酒酒醅中乳酸高产菌株的筛选及乳酸的分离纯化

该研究以分离自清香型白酒酒醅的10株乳酸菌为研究对象，采用溶钙圈法和液体发酵法从中筛选高产乳酸菌株，并对其产乳酸条件进行考察；然后通过活性炭和离子交换柱对乳酸进行分离纯化，并通过高效液相色谱（HPLC）法检测乳酸纯度。结果表明，植物乳杆菌（Lactobacillus plantarum）SL32-2为高产乳酸的菌株，其在高粱糖化液中产乳酸的最佳发酵温度和初始pH值分别为35 ℃和7.0。活性炭对其发酵液的最适处理条件为活性炭添加量1.5 g/100 mL、处理温度60 ℃、处理时间2 h，此时脱色率、脱糖率和脱蛋白率分别为72.65%、3.75%和85.81%。经离子交换柱进一步纯化后，乳酸总得率为51.12%，其中阴离子交换柱的洗脱液中乳酸纯度较高。     

Comparative evaluation of bacterial cellulose (nata) as a cryoprotectant and carrier support during the freeze drying process of probiotic lactic acid bacteria

Nata or bacterial cellulose produced by Acetobacter xylinum was compared for its cryoprotective and carrier support potential for probiotic lactic acid bacteria against other established cryoprotectants like 10% skim milk, calcium alginate encapsulation or 0.85% physiological saline and distilled water. Individual lactic acid bacteria were grown in MRS broth in the presence of nata cubes or the bacterial suspension mixed with either powdered bacterial cellulose (PBC), 10% skim milk, saline or distilled water and freeze dried. These freeze dried cells were stored at temperatures of either 30 °C or 4 °C and periodically checked for viability. The freeze dried cells on carrier supports were directly used to prepare fermented milks to establish the activity of these cultures. Scanning electron microscopy was employed to visualize the support matrix with the attached lactic acid bacteria. The freeze drying process resulted in a 3.0 log cycle reduction in the colony forming units as compared to the original cell suspension in the case of all the lactic acid bacteria. The growth of lactic acid bacteria in the presence of bacterial cellulose (nata) offers a convenient and easy method to preserve bacteria for short durations and use it as a support to carry out other fermentation processes.     

Effect of lactic acid fermentation on antioxidant, texture, color and sensory properties of red and green smoothies

Weissella cibaria, Lactobacillus plantarum, Lactobacillus sp. and Lactobacillus pentosus were variously identified from blackberries, prunes, kiwifruits, papaya and fennels by partial 16S rRNA gene sequence. Representative isolates from each plant species were screened based on the kinetics of growth on fruit juices. A protocol for processing and storage of red and green smoothies (RS and GS) was set up, which included fermentation by selected lactic acid bacteria starters and exo-polysaccharide producing strains. Starters grew and remained viable at ca. 9.0 log cfu g⁻¹ during 30 days of storage at 4 °C. No contaminating Enterobacteriaceae and yeast were found throughout storage. Values of soluble solids, total titratable acidity and viscosity distinguished started RS and GS compared to spontaneously (unstarted) fermented smoothies. Color difference dE∗_ab and browning index were positively affected by lactic acid fermentation. Consumption of carbohydrates by lactic acid bacteria was limited as well as it was the lactic fermentation. Consumption of malic acid was evident throughout storage. Polyphenolic compounds and, especially, ascorbic acid were better preserved in started RS and GS compared to unstarted samples. This reflected on the free radical scavenging activity. A statistical correlation was only found between the level of ascorbic acid and free radical scavenging activity. As shown by a ?rst-order equation, the rate of degradation of ascorbic acid through storage were found to be higher in the unstarted compared to started RS and GS. Fermentation by lactic acid bacteria clearly improved the sensory attributes of RS and GS.     

乳酸菌和酵母菌混合发酵制备谷物发酵饮料的工艺研究

以大麦芽、小米、赤小豆、燕麦为谷物原料,酵母菌和乳酸菌为发酵菌种混合发酵制备谷物发酵饮料。以感官评分为评价指标,先通过单因素试验研究了乳酸菌接种量、发酵温度等5个因素对谷物发酵饮料品质的影响,筛选出了乳酸菌接种量、发酵温度、酵母接种量三个主要影响因素,再通过响应面法进行了工艺优化。在优化其工艺条件的基础上,对谷物发酵液进行了调配。结果表明,最佳制备工艺为发酵温度38 ℃,乳酸菌接种量3.3%,酵母菌接种量0.7%,原麦汁浓度8 °P。添加发酵液50%,三氯蔗糖0.025%,槐花蜜5%制得的谷物发酵饮料感官评分为97分,酒精度为0.12%vol,接受度较高,可推广应用。     

酵母菌与乳酸菌发酵对小米淀粉粘度的影响

自然发酵受环境和微生物的影响大,难实现发酵产品的大规模生产。故研究自然发酵优势菌对小米淀粉的影响很有必要。选取内蒙古赤峰生产的黄金苗小米为原料,利用自然发酵纯化的酵母菌与乳酸菌为菌种进行纯种发酵96 h,并且与自然发酵后的小米淀粉比较,分析淀粉的粘度、衰减值和回生值的变化。采用0.2 g/100 m L的Na OH溶液提取3 h的方法来提取发酵后小米中的淀粉,并对其发酵液中固形物的含量、p H、淀粉的粘度特性、偏光十字进行测定。结果表明,三种发酵方法所得的发酵液中总固形物的含量都增加;较自然发酵相比,发酵前24 h乳酸菌和酵母菌发酵液中的p H下降迅速,之后变化缓慢;淀粉粘度特性表明,乳酸菌和酵母菌发酵终止时,其粘度的起始温度、衰减值、回生值较自然发酵相比都下降,峰值粘度较自然发酵相比都上升,乳酸菌发酵和酵母菌发酵的最终粘度与自然发酵相比有所增加,偏光十字显示无论是自然发酵酵母菌发酵还是乳酸菌发酵,发酵后的淀粉颗粒仍具有偏光十字,说明发酵未改变淀粉的结晶结构。      

Use of spent brewer's yeast in L‐(+) lactic acid fermentation

The application of by‐products from the brewing industry in lactic acid (LA) production was investigated in order to replace expensive nitrogen sources (such as yeast extract) with cheaper and renewable nitrogenous materials such as brewer's yeast (BY). In this study, brewer's spent grain (BSG) hydrolysate was used for L‐(+)‐LA fermentation by Lactobacillus rhamnosus ATCC 7469. The effect of pH control during the fermentation and the addition of various BY contents (5–50 g/L) in BSG hydrolysate on fermentation parameters was evaluated. BY addition significantly increased free amino nitrogen (FAN) concentration (by 25.2% at 5 g/L to 616% at 50 g/L). A strong positive correlation between FAN concentration in the hydrolysate and concentration of L‐(+)‐LA produced was observed (correlation coefficient of 0.913). A high cell viability of L. rhamnosus ATCC 7469 (1.95–3.32 × 10⁹ CFU/mL at the end of fermentation) was achieved in all fermentations with the addition of brewer's yeast. The addition of BY increased L‐(+)‐lactic acid yield and volumetric productivity up to 8.4% (5 g/L) and 48.3% (50 g/L). The highest L‐(+)‐LA yield (89%) and volumetric productivity (0.89 g/L h^?1) were achieved in fermentation of BSG hydrolysate with 50 g/L of BY. © 2019 The Institute of Brewing & Distilling     

糠醛渣的预处理、酶解优化及同步糖化发酵

以碱性过氧化氢（AHP）预处理的糠醛渣为原料进行酶解,有效地提高糖转化率。结果表明,在10%底物浓度下,24 h葡萄糖的 转化率达到了96.46%,比未预处理组提高了37.44%。 通过Mixture设计,确定了酶解的最优加酶量,即纤维素酶96%、半纤维素酶2%、 果胶酶2%。 对AHP预处理过的糠醛渣进行水洗能有效去除酶活抑制物,较未水洗组,24 h葡萄糖转化率提升了18.23%。 通过正交试验 优化糠醛渣同步糖化发酵（SSF）生成乙醇的条件为：反应温度38 ℃,pH 4.6,加酶量30 mg酶蛋白/g葡聚糖,酵母接种量10%。 在此最佳 条件下,糠醛渣同步糖化发酵96 h生成乙醇为理论转化率的88.64%。     

Enrichment of bioactive isoflavones in soymilk fermented with β-glucosidase-producing lactic acid bacteria

This study was undertaken to investigate the possible application of β-glucosidase-producing lactic acid bacteria as a functional starter cultures to obtain the bioactive isoflavones, genistein and daidzein, in fermented soymilk. Four strains – Lactobacillus plantarum KFRI 00144, Lactobacillus delbrueckii subsp. lactis KFRI 01181, Bifidobacterium breve K-101 and Bifidobacterium thermophilum KFRI 00748 – among the 31 lactic acid bacteria tested for β-glucosidase activity using ρ-nitrophenyl-β-d-glucopyranoside as the substrate were selected. Acid development, viable populations, and quantification of isoflavones using HPLC were performed at 0, 24, and 48 h of incubation at 37 °C. The significant bioconversion (P < 0.001) of the glucoside isoflavones into their bioactive aglycones in soymilk fermented with four β-glucosidase-producing strains, with an average 7.1-fold increase of aglycones (daidzein + genistein) was observed. There appeared to be correlations between the level of growth and β-glucosidase activity of each strain, and the hydrolysis of conjugated isoflavones in soymilk fermentation. Lactobacillus sp. were able to readily proliferate in soymilk than Bifidobacterium sp. (P < 0.05) and therefore completed more rapidly the hydrolysis of glucoside isoflavones.The present study indicates that four β-glucosidase-producing lactic acid bacteria have great potential for the enrichment of bioactive isoflavones in soymilk fermentation.