-乳酸的研究

从所选取的产l-乳酸的4株菌中筛选出一株性能优良、糖利用率和乳酸产量较高的菌种作为试验用菌种。对影响乳酸菌发酵大豆秸秆酶解物制备l-乳酸的因素进行了研究,影响大豆秸秆酶解液发酵的主要因素是菌种类型、底物糖浓度、接种量、温度及pH值。结果表明:干酪乳酸菌是较适宜的发酵菌种,较适宜的发酵条件为:发酵温度30℃,接种量10%,pH值5.5。随着底物糖含量的增加,乳酸产率相应增大,在实验范围内,乳酸菌发酵所产乳酸的产率达到80%。     

高光学纯度L-乳酸发酵工艺研究

乳酸发酵在线近红外光谱(NIR)的近红外分析技术,是通过过程分析仪器,采用非接触式的方法在线监测乳酸发酵。通过建立近红外光谱仪监测数据模型,能便捷快速地对乳酸发酵过程调控。乳酸发酵采用大型发酵罐套接菌种的方式接种,可以明显提升发酵效果。确定了400 t发酵罐套接菌种量28%时,L-乳酸光学纯度和收率达到最高,分别是99.8%和98.57%,乳酸发酵效果最佳。     

D-乳酸制备研究进展

高光学纯度D-乳酸在聚乳酸高性能材料方面的应用带动了D-乳酸生产工艺研究的发展。本文综述了D-乳酸的应用、光学纯度的分析方法以及制备工艺,着重介绍了D-乳酸的生产菌种选育和D-乳酸发酵的国内外研究进展,D-乳酸基因工程菌改造也已形成一定的竞争力,并指出开发光学纯度高、产量高、转化率高,发酵周期短和底物利用范围广的D-乳酸高产菌还可进一步提升D-乳酸的制备技术。     

固定化米根霉发酵生产乳酸的研究进展

根霉属中的米根霉是迄今认为生产L-乳酸较为理想的菌种.利用游离的米根霉发酵乳酸时会产生菌种利用率低、生产效率低等一系列不足,因此展开了菌体固定化发酵的研究.目前米根霉固定化发酵工程的研究主要集中于载体的选择和新型生物反应器的研制.本文对此研究进展作了综合评述与讨论,认为米根霉固定化发酵乳酸可以进一步降低生产成本,提高乳酸产率.     

玉米原料生产L-乳酸的几个技术问题

论述用玉米发酵法生产L-乳酸及对其优良菌种的选育;玉米原料的综合利用和L-乳酸发酵设备、提取工艺的改进等。并对L-乳酸的深加工和应用领域作了简要介绍。     

玉米浆为有机氮源的L-乳酸发酵的研究

利用细菌厌氧发酵生产L-乳酸,以降低L-乳酸生产成本为主要目的,实验以玉米浆为有机氮源,以硫酸铵为主要无机氮源,研究了不同接种量对发酵过程的影响;并就以玉米浆替代酵母粉、豆粕水解液、生物素为有机氮源的L-乳酸发酵进行了对比研究实验,实验证明了玉米浆做为有机氮源用于L-乳酸发酵的可行性。在保证生产能力的同时,使用玉米浆为有机氮源对进一步降低L-乳酸生产成本,减少玉米浆对环境的污染进行了探索。     

高浓度L-乳酸发酵菌种的选育与工艺优化

L-乳酸是一种重要的有机酸,又是生产生物可降解材料聚乳酸的原料。通过对细菌发酵法生产工艺的研究,选育出一株生产高浓度L-乳酸的发酵菌种——嗜热芽孢杆菌,并以此为基础,经过优化种子培养基和发酵培养基,最高发酵产酸达到了180g/L的水平,光学纯度达98.5%以上,发酵转化率达到92%以上。     

原位分离技术应用于乳酸发酵的研究进展

生物发酵法是目前乳酸生产的主要方法,但乳酸发酵随着发酵过程会产生产物抑制,若不想办法消除产物抑制会造成严重抑制发酵进行。传统工艺加入中和剂产生的盐离子浓度提高同样抑制细胞活性。而原位分离技术在移走代谢产物同时不产生更多离子,是解决产物抑制的有效解决方案。此外原位分离技术移走发酵产物后,剩余发酵液可以循环进行发酵,使连续发酵成为可能。目前可应用于原位分离技术的分离方式有膜分离、萃取、吸附等,以及多种分离方式的结合。应用原位分离技术乳酸发酵,可为连续发酵乳酸提供技术基础,是今后乳酸工业大规模生产的技术保证。     

10000吨/年D-乳酸项目

<正>该项目位于安徽省蚌埠市固镇经济开发区,由安徽丰原发酵技术工程研究有限公司投资建设,建设年产10000吨/年D-乳酸生产线及其配套装置,项目采用生物发酵法生产D-乳酸,以葡萄糖为底物,使用D-乳酸菌种,经发酵、提取、精制等工序获得D-乳酸产品。项目总投资13700万元。     

发酵液中乳酸的分离提取研究进展

乳酸是合成聚乳酸的原料,生物法制备乳酸是目前工业上生产乳酸的主要方法。但乳酸发酵液成分复杂,后续的分离提纯过程成了制约乳酸生产的技术瓶颈和难点,也决定着乳酸的品质与收率。本文对乳酸发酵液的主要的分离提取工艺进行了介绍,包括结晶分离技术、酯化水解法、萃取法、分子蒸馏法、膜分离法、吸附法及与发酵耦合的原位分离技术。并提出单一的分离技术很难有效提取乳酸,需将多种技术集成、改良提纯工艺路线。其中,将各种新型高效的集成技术与发酵过程的有机结合,实现连续或半连续的发酵过程,可提高乳酸产率和产品质量,有望形成高效率、高品质、低污染、低能耗、可工业化的乳酸提纯工艺路线。     

生物质转化制备乳酸及其酯类物质研究进展

乳酸是重要的精细化工中间体,在食品、医药、日化及可降解材料等领域具有重要的应用.利用农林废弃物为原料转化制备乳酸,不仅能够充分利用生物质资源,更能缓解乳酸供需矛盾,对推动碳减排及绿色发展具有重要意义.分别从微生物发酵法和化学催化法对生物质转化制备乳酸(酯)的最新研究进展进行了综述,并对当前阶段制约乳酸生产的各方面因素进行了分析总结,最后全面比较了这两种方法的优缺点,展望了生物质转化制备乳酸潜在研究方向、存在的机遇和面临的挑战.     

厨余垃圾的资源化技术

介绍了厨余垃圾的来源与特征,讨论了厨余垃圾的资源化技术:主要包括堆肥、厌氧发酵、真空油炸、蚯蚓生物处理、乳酸发酵以及生物制氢等,其中家庭垃圾处理机和小容量垃圾系列处理机堆肥技术具有费用低和实现源头减量化等优点。生物制氢、厌氧发酵和燃料电池发电系统的开发研究,为废物变清洁能源开辟了新的途径。此外,利用厨余垃圾制取乳酸,进而合成生物降解性塑料(聚乳酸)的技术,可为治理困扰人类的"白色污染"作出贡献。     

A comparative study of the growth of lactic acid bacteria in a pilot scale membrane bioreactor

BACKGROUND: A central problem in the production of lactic acid bacteria (LAB) is the low productivity conventional batch systems due to end product inhibition. This work investigated the impacts of the membrane bioreactor (MBR) on the growth of four industrially important LAB and compared the growth in pH controlled STR using Lactobacillus buchneri, L. brevis, Oenococcus oeni, and Bifidobacterium longum. RESULTS: The four LAB were grown in a pH‐controlled STR batch culture and this was compared with perfusion culture of the MBR. The growth of LAB in MBR produced a far more intensive production of cells with great volumetric productivity and high cell concentrations compared with STR cultures. Total cell concentration in perfusion culture of LAB reached 13 to 23 g DCW L^?1 up to 14 times higher than those obtained in the STR cultures. Overall volumetric biomass production rates in the MBR increased from 10 to 33 times that in the STR, and were organism dependent. CONCLUSION: The MBR has considerable potential for enhanced production of LAB. Limitations to growth and growth rate during perfusion culture of LAB in the MBR were from gas bubbles produced or membrane fouling. Further improvements in productivities are possible with careful design of the media, the MBR reactor and the performance characteristics of the LAB. Copyright © 2010 Society of Chemical Industry     

Use of 1‐hexyl‐3‐methylimidazolium bromide ionic liquid in the recovery of lactic acid from wine

BACKGROUND: Lactic acid has many different applications in a variety of industries including the food, cosmetics, packaging, leather and chemical industries. Current methodologies for lactic acid production are lengthy and complicated and more efficient methods are being sought. Some organic wastes contain lactic acid and our work investigates the use of ionic liquids (ILs) in the efficient and selective extraction of lactic acid from organic waste using wine as a model system. The ionic liquid was chosen based on its ability to selectively solvate and separate lactic acid from the remaining bulk waste material. RESULTS: Several ILs including 1‐hexyl‐3‐methylimidazolium chloride (hmimCl), 1‐hexyl‐3‐methylimidazolium bromide (hmimBr), 1‐hexyl‐3‐methylimidazolium iodide (hmimI) and N‐hexylpyridinium iodide (hpyrI) have been synthesized in high yield (68‐95%) using microwave technology. Lactic acid is soluble in each of the ILs synthesized with optimum results achieved with hmimBr where lactic acid is miscible in all proportions. HmimBr has been used to successfully separate and extract lactic acid from wine as confirmed by FTIR spectroscopy. Furthermore, it has been possible to recover the IL for recycle in subsequent extraction cycles where the efficiency for the extraction process increases with each recycle. CONCLUSION: HmimBr has been used for the first time in a novel process for the separation and recovery of lactic acid from wine, as confirmed by FTIR spectroscopy. This work demonstrates a novel process which can be applied to the recovery of lactic acid from organic waste. Copyright © 2012 Society of Chemical Industry     

Studies on the synthesis and thermal properties of copoly(L‐lactic acid/glycolic acid) by direct melt polycondensation

A two‐step direct copolymerization process of L ‐lactic acid (L ‐LA)/glycolic acid (GA) was developed. The first step was to produce an oligomer of L ‐LA/GA and then the oligomer was polymerized with binary catalyst tin chloride dihydrate/p‐toluenesulfonic acid. In this way, the copoly(L ‐LA/GA) (PLGA), without any organic solvent, was synthesized directly. The thermal properties and solubility in chloroform of PLGA were studied by DSC and NMR. The results showed that the melting point of PLGA decreases with increasing mole fraction of GA units in copolymer. In addition, the melting point of polymer also decreased with increasing degree of racemization of polymer. The solubility of PLGA in chloroform decreased with the increase of the average lengths of the glycolic acid units. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2163–2168, 2004     

乳酸菌发酵甘蔗糖蜜产乳酸的培养条件优化

乳酸是有广泛应用的有机酸,廉价原料是降低乳酸生产成本的重要因素。以实验室前期筛选的植物乳杆菌sy4为出发菌株研究了利用甘蔗糖蜜生产乳酸的培养条件。在确定发酵温度和初始pH后,通过Plackett-Burman实验和中心复合实验优化乳酸发酵条件。结果表明：植物乳杆菌sy4乳酸发酵的最适条件为温度32℃、60h、初始pH 6.5;Plackett-Burman实验表明酵母提取物、糖蜜和碳酸钙是影响乳酸产量的主要因素;中心复合实验得到三因素的最优组合为：酵母提取物13.19g/L、糖蜜476.63g/L和碳酸钙134.82g/L,确定了最适发酵培养基。在此条件下乳酸产量为（145.53±1.24） g/L,与模型预测值147.23g/L接近。本研究为以甘蔗糖蜜为原料生产乳酸提供了技术支持。     

Selective conversion of glucose into lactic acid and acetic acid with copper oxide under hydrothermal conditions

Biomass as a source for chemicals production attracts growing attention due to the decreasing storage of fossil fuels and global warming caused by emission of CO₂. In this study, conversion of glucose with copper oxide (CuO) was studied under alkaline hydrothermal conditions using a batch reactor and continuous flow reactor. CuO, as an oxidant, greatly improves the yields of lactic acid (LA) and acetic acid from glucose and was reduced into Cu₂O and Cu. Selective production of LA with the highest yield of 59% and acetic acid with the highest yield of 32% can be achieved by controlling reaction time, temperature, and addition of CuO. A possible mechanism of conversion of glucose with CuO was proposed. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2096–2104, 2013     

Hydrothermal conversion of fructose to lactic acid and derivatives: Synergies of metal and acid/base catalysts

With increasing strict regulation on single-use plastics, lactic acid (LA) and alkyl lactates, as essential monomers for bio-degradable polylactic acid (PLA) plastic products, have gained worldwide attention in both academia and industry. While LA is still dominantly produced through fermentation processes from start, chemical synthesis from cellulosic biomass remains a grand challenge, owing to poor selectivity in activating C-H and C-C bonds in sugar molecules. To our best knowledge, recent publications have been focused on hydrothermal conversion of glucose to LA, while this review summarizes the highlights on direct thermal conversion of fructose as starting material to LA and derivatives. In particular, the synergies of metal/metal cations and acid/base catalysts will be critically revised on retro-aldol and dehydration reactions. This work will provide insights into rational design of active and selective catalysts for the production of carboxylic acids from biomass feedstocks.     

In situ reactive extraction of lactic acid from fermentation media

Extractive lactic acid fermentation was investigated in the presence of sunflower oil and Alamine‐336 (with oleyl alcohol as the diluent solvent). Lactic acid was produced in various media at 37 °C using Lactobacillus delbrueckii (NRRL‐B 445). First, the effects of oleyl alcohol (33.3%, v/v), immobilisation, and immobilisation in the presence of sunflower oil (5, 10, 15%, v/v) on lactic acid production were investigated. It was found that oleyl alcohol did not affect production while addition of sunflower oil increased lactic acid production from 10.22 to 16.46 gdm^?3. On the other hand, a toxic effect was observed for oleyl alcohol solutions containing 15–50% (v/v) Alamine‐336. A maximum total lactic acid concentration of 25.59 gdm^?3 was obtained when an oleyl alcohol solution containing 15% (v/v) Alamine together with immobilised cells with 15% (v/v) sunflower oil was used. This value was about 2.5 times that obtained from fermentation without organic solutions. © 2001 Society of Chemical Industry     

Extraction of lactic acid into sunflower oil and its recovery into an aqueous solution

Demand for lactic acid is growing, especially, for its use in the production of biodegradable polymer (polylactate). The current method of production and separation of lactic acid is both expensive and unsustainable. This is partly due to the cost and lower efficiency of the current method for separating the lactic acid product from the fermentation media. Therefore, the development of alternative technology that will offer efficiency, economic and environmental benefits is of great importance. One of the promising technologies for recovery of lactic acid from fermentation broth is reactive liquid–liquid extraction. In this paper, processes based on reactive extraction of lactic acid into an organic phase and its recovery into an aqueous phase is examined. The percentages of extraction and recovery are determined by using a small pilot-scale microporous hollow-fibre membrane module (HFMM). Firstly, equilibrium experiments were conducted using organic solutions consisting of Aliquat 336 and trioctylamine (as carriers) and tributyl phosphate and sunflower oil (as solvents) The values of the distribution co-efficient (defined as a ratio of the concentration of lactic acid extracted over that remaining in the aqueous solution at equilibrium) were obtained as a function of feed pH (range 4.0–6.5), composition of the organic phase (ratio of carrier to solvent) and temperature (range 8–40°C). The best extraction was obtained with the organic phase of 15wt% tri-octylamine (TOA), 15% aliquat 336 dissolved in 35 wt% tri-butyl phosphate (TBP) and 35% sunflower oil. The percentage extraction from 0.1 M was approx. 70% after 4 h at pH 5.0 and at 35°C at a recirculating flow rate of 15–20 L/h. Lactic acid was reextracted from the organic phase by using 0.5 M sodium carbonate solution and approx. 90% recovery was obtained in 4 h. These results demonstrate that good extraction and recovery of lactic acid in the hollow-fibre membrane are possible. Also because of its potential for application in situ the process would allow to maintain lactic acid concentration at low levels during the fermentation and to improve productivity by suppressing the product inhibition effects.