Comparative of Lignocellulosic Ethanol Production by Kluyveromyces marxianus and Saccharomyces cerevisiae

The world faces a progressive depletion of its energy resources, mainly fossil fuels based on non-renewable resources. At the same time, the consumption of energy grows at high rates, and the intensive use of fossil fuels has led to an increase in the generation of gaseous pollutants released into the atmosphere, which has caused changes in the global climate. The lignocellulosic bioethanol is considered as a promising alternative for use as fuel ethanol. However, one of the main problems in producing ethanol is toxic compounds generated during hydrolysis of lignocellulosic wastes; these compounds cause a longer lag phase and irreversible cell damage to the microorganisms used in the fermentation step. These conditions of fermentation affect the productivity and the economic feasibility of the lignocellulosic ethanol production process. In this context, many efforts had been carried out to improve the capacity of volumetric ethanol productivity of the yeast. The yeast Saccharomyces cerevisiae is commonly employed in industrial ethanol production. However non-Saccharomyces yeast as Kluyveromyces marxianus can produce alcohols at similar or higher levels than S. cerevisiae and on inhibitory conditions

Second-Generation Bioethanol Production through a Simultaneous Saccharification-Fermentation Process Using Kluyveromyces Marxianus Thermotolerant Yeast

Due to the present renewable fuels demand increase, reduction of second-generation bioethanol production cost is pursued, since it is considered the most promising biofuel, but not yet economically viable. A proposed solution is its production through a simultaneous saccharification and fermentation process (SSF); however, it is necessary to apply temperatures above 40°C, which reduce the viability of traditional ethanologenic yeasts. As consequence, the use of thermotolerant ethanologenic yeast has been suggested, among which the yeast Kluyveromyces marxianus stands out. This chapter addresses the production of second-generation bioethanol through the SSF process, emphasizing the potential of K. marxianus to transform lignocellulosic biomass as agave bagasse. As result, it is proposed to direct the second-generation bioethanol production to the SSF process employing thermotolerant yeasts, to increase process productivity, and addressing the economic barriers

Improvement of a Specific Culture Medium Based on Industrial Glucose for Carotenoid Production by Xanthophyllomyces dendrorhous

In this study, a low-cost chemically defined (CD) culture medium was proposed and evaluated with the aim of replacing culture media such as yeast mold (YM) and yeast peptone dextrose (YPD), commonly used for growth and carotenoid production by Xanthophyllomyces dendrorhous. Initially, the CD culture medium was compared to the YM and YPD. The growth in optical density (OD) and carotenoid production (mg/L) of the cultures reached 4.88, 6.76, 5.79, and 0.67, 0.92, and 0.69, respectively. The CD culture served as the basis of an improved specific culture medium containing industrial glucose. Additionally, in this new formulation, vitamins, glutamate, and other compounds were evaluated. Industrial glucose more than doubled carotenoid production; however, the addition of vitamins was not essential for X. dendrorhous cultivation. Moreover, glutamate and Na2HPO4 proved to be highly significant factors (p-value < 0.05), increasing carotenoid biosynthesis from 0.67 to 1.33 mg/L. The specific culture was successfully used in a bioreactor at 2 L and 110 L pilot-scale levels, increasing carotenoid production up to 2 mg/L. It was demonstrated that the CD-specific culture medium is an efficient alternative to conventional culture media to carry out carotenoid production at the laboratory and pilot levels, with promising potential for industrial scaling

Effect of Carbon Sources in Carotenoid Production from Haloarcula sp. M1, Halolamina sp. M3 and Halorubrum sp. M5, Halophilic Archaea Isolated from Sonora Saltern, Mexico

The isolation and molecular and chemo-taxonomic identification of seventeen halophilic archaea from the Santa Bárbara saltern, Sonora, México, were performed. Eight strains were selected based on pigmentation. Molecular identification revealed that the strains belonged to the Haloarcula, Halolamina and Halorubrum genera. Neutral lipids (quinones) were identified in all strains. Glycolipid S-DGD was found only in Halolamina sp. strain M3; polar phospholipids 2,3-O-phytanyl-sn-glycerol-1-phosphoryl-3-sn-glycerol (PG), 2,3-di-O-phytanyl-sn-glycero-1-phospho-3′-sn-glycerol-1′-methyl phosphate (PGP-Me) and sodium salt 1-(3-sn-phosphatidyl)-rac-glycerol were found in all the strains; and one unidentified glyco-phospholipid in strains M1, M3 and M4. Strains M1, M3 and M5 were selected for further studies based on carotenoid production. The effect of glucose and succinic and glutamic acid on carotenoid production was assessed. In particular, carotenoid production and growth significantly improved in the presence of glucose in strains Haloarcula sp. M1 and Halorubrum sp. M5 but not in Halolamina sp. M3. Glutamic and succinic acid had no effect on carotenoid production, and even was negative for Halorubrum sp. M5. Growth was increased by glutamic and succinic acid on Haloarcula sp. M1 but not in the other strains. This work describes for first time the presence of halophilic archaea in the Santa Bárbara saltern and highlights the differences in the effect of carbon sources on the growth and carotenoid production of haloarchaea

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)