Didak Ljubas Blanka, Novak Mario, Trontel Antonija, Rajković Ana, Kelemen Zora, Marđetko Nenad, Grubišić Marina, Pavlečić Mladen, Tominac Vlatka Petravić, Šantek Božidar
Department of Biochemical Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia.
Front Microbiol. 2022 Mar 4;13:812457. doi: 10.3389/fmicb.2022.812457. eCollection 2022.
Brewers' spent grains (BSG) are a by-product of the brewing industry that is mainly used as feedstock; otherwise, it has to be disposed according to regulations. Due to the high content of glucose and xylose, after pretreatment and hydrolysis, it can be used as a main carbohydrate source for cultivation of microorganisms for production of biofuels or biochemicals like 2,3-butanediol or lactate. 2,3-Butanediol has applications in the pharmaceutical or chemical industry as a precursor for varnishes and paints or in the food industry as an aroma compound. So far, , , , and are being used and investigated in different bioprocesses aimed at the production of 2,3-butanediol. The main drawback is bacterial pathogenicity which complicates all production steps in laboratory, pilot, and industrial scales. In our study, a gram-positive GRAS bacterium DSM 742 was used for the production of 2,3-butanediol. Since this strain is very poorly described in literature, bacterium cultivation was performed in media with different glucose and/or xylose concentration ranges. The highest 2,3-butanediol concentration of 18.61 g l was achieved in medium with 70 g l of glucose during 40 h of fermentation. In contrast, during bacterium cultivation in xylose containing medium there was no significant 2,3-butanediol production. In the next stage, BSG hydrolysates were used for bacterial cultivation. DSM 742 cultivated in the liquid phase of pretreated BSG produced very low 2,3-butanediol and ethanol concentrations. Therefore, this BSG hydrolysate has to be detoxified in order to remove bacterial growth inhibitors. After detoxification, bacterium cultivation resulted in 30 g l of lactate, while production of 2,3-butanediol was negligible. The solid phase of pretreated BSG was also used for bacterium cultivation after its hydrolysis by commercial enzymes. In these cultivations, DSM 742 produced 9.8 g l of 2,3-butanediol and 3.93 g l of ethanol. On the basis of the obtained results, it can be concluded that different experimental setups give the possibility of directing the metabolism of DSM 742 toward the production of either 2,3-butanediol and ethanol or lactate.
啤酒糟是酿酒工业的一种副产品，主要用作原料；否则，必须按照规定进行处理。由于葡萄糖和木糖含量高，经过预处理和水解后，它可以用作培养微生物以生产生物燃料或生化物质（如2,3-丁二醇或乳酸）的主要碳水化合物来源。2,3-丁二醇在制药或化学工业中用作清漆和油漆的前体，或在食品工业中用作香料化合物。到目前为止， 、 、 和 正在不同的生物过程中被使用和研究，旨在生产2,3-丁二醇。主要缺点是细菌致病性，这使得实验室、中试和工业规模的所有生产步骤都变得复杂。在我们的研究中，使用了一种革兰氏阳性的公认安全细菌DSM 742来生产2,3-丁二醇。由于该菌株在文献中描述很少，因此在不同葡萄糖和/或木糖浓度范围的培养基中进行细菌培养。在发酵40小时期间，在含有70 g/l葡萄糖的培养基中获得了最高2,3-丁二醇浓度18.61 g/l。相比之下，在含木糖的培养基中进行细菌培养时，没有显著的2,3-丁二醇产生。在下一阶段，使用啤酒糟水解产物进行细菌培养。在预处理啤酒糟的液相中培养的DSM 742产生的2,3-丁二醇和乙醇浓度非常低。因此，必须对这种啤酒糟水解产物进行解毒，以去除细菌生长抑制剂。解毒后，细菌培养产生了30 g/l的乳酸，而2,3-丁二醇的产量可以忽略不计。预处理啤酒糟的固相在通过商业酶水解后也用于细菌培养。在这些培养中，DSM 742产生了9.8 g/l的2,3-丁二醇和3.93 g/l的乙醇。根据获得的结果，可以得出结论，不同的实验设置使得有可能将DSM 742的代谢导向生产2,3-丁二醇和乙醇或乳酸。
