The focus of this dissertation centers on the development and applications of gas chromatography/mass spectrometry and capillary electrophoresis methodologies to quantify monomeric compositions of the β-O-4 linkages in lignin. Pretreatment is a required step in the utilization of lignocellulosic biomass for biofuels. Lignin is the target of pretreatment because it hinders the accessibility of enzymes and chemicals to cellulose. The effects of pretreatment are commonly assessed utilizing enzymatic saccharification and lignin assays. However, these techniques do not elucidate the effects of pretreatment on the monomeric make up of lignin. The overarching hypothesis of this dissertation is that changes in individual monolignol content upon pretreatment can be observed from quantification. To test the hypothesis, a pretreatment, solution phase Fenton chemistry, was conducted on various lignocellulosic biomass feedstocks. Enzymatic saccharification studies showed a significant increase in glucose production upon Fenton pretreatment, however, lignin assays did not show a significant decrease in lignin content. Project two of this dissertation aimed to synthesize analytical standards in order to develop a quantitative thioacidolysis technique. The successful synthesis of the three arylglycerols were conducted utilizing and epoxidation reaction scheme which was hypothesized to produce a single diastereomer, as supported by GC/MS and chiral CE analysis. Upon method development, a quantitative thioacidolysis GC/MS method was applied to untreated and Fenton treated biomass. Results from this project revealed there was no significant change in the three lignin monomers. To verify the method, quantitative thioacidolysis GC/MS method was applied to a pretreatment method known to degrade lignin, alkaline peroxide pretreatment. The results of this project showed a significant change in monolignol concentrations upon alkaline peroxide pretreatment. Analytical degradative techniques, such as thioacidolysis, has traditionally assessed lignin as monomeric ratios. However, as this dissertation showed, upon alkaline peroxide pretreatment, no significant change was seen in the monomeric ratios, but there was a significant difference in all three monolignol concentrations. These results support the overall hypothesis that changes in individual monolignol content upon pretreatment can be observed from quantification. The works of this dissertation provides an analytical method which contributes to the elucidation of lignin.

This study investigated the fate of lignocellulosic biomass (wheat-feed and perennial rye grass) in different anaerobic digestion systems, evaluating the role of substrate specificity on the pattern of degradation. The two-stage (biohydrogen-biomethane) anaerobic system was found to be more effective in the degradation of lignocellulose, when compared to the conventional single-stage system. The perennial rye grass substrate possessed about 21% higher holocellulose concentration when compared to the wheat-feed; its exploitation in the acidogenic digestion was however poor, resulting in a 2.9% lower biogas yield in a equivalent two-stage system. The study therefore developed a treatment technique involving the use of cellulase and ferulic acid esterase enzyme combinations for the treatment of perennial rye grass. The enzyme cocktail at 0.202 ml enzyme/g VS added resulted in efficient bioconversion of the complex polymers to soluble carbohydrates, evident in the yield increase of soluble COD, to 321.0±10.9 mg/gVS, a 393.2% yield increase, when compared to the no enzyme added control. The yield of bio-hydrogen after enzymatic addition was 48ml/gVS, 335% higher when compared to the alkaline treatment; and more than seven fold higher than the yield obtained from the fermentation with no pre-treatment. The acetate to butyrate ratio varied from 4:1, when no pre-treatment was used, to 2:1when alkaline pre-treatment was used, then to 1:1 after the enzymatic treatment. The downstream effect of the prior hydrolysis on the subsequent processes to acidogenic fermentation like biomethane and PHA production and lignin recovery were also investigated. The hydrogenic/acidogenic fermentation resulted in methane yield improvement of 45.7%. The study shows that the more effective a hydrolysis procedure is in the depolymerisation of complex polymers, the greater the accumulation of PHA in the PHA biosynthesis operations. The enhanced hydrogenic /acidogenic fermentation having effectively degraded the holocellulose component of the perennial rye grass substrate ensured that relatively high quality lignin was obtained in an Organosolv lignin-extraction procedure. FT-IR profile show less contamination of polysaccharides and proteins in the lignin extracted from the enzymatically enhanced acidogenic fermentation. An evaluation of the economic viability of the investigated secondary processes showed that direct integrations of those processes to the biohydrogen process may not be as economically advantageous, when compared to a 2nd -stage biomethanation system.

Doctor of Philosophy / Grain Science and Industry / Praveen V. Vadlani / Lignocellulosic biomass feedstocks are a sustainable resource required for rapid growth of bio-based industries. An integrated approach, including plant breeding, harvesting, handling, and conversion to fuels, chemicals and power, is required for the commercial viability of the lignocellulosic-based biorefineries. Optimization of conversion processes, including biomass pretreatment and hydrolysis, is a challenging task because of the distinct variations in composition and structure of biopolymers among biomass types. Efficient fermentation of biomass hydrolyzates comprising of different types of sugars is challenging. The purpose of this doctoral research was to evaluate and optimize the various processing steps in the entire the biomass value chain for efficient production of advanced biofuels and chemicals from diverse biomass feedstocks. Our results showed that densification of bulky biomass by pelleting to better streamline the handling and logistic issues improved pretreatment and hydrolysis efficiencies. Alkali pretreatment was significantly more effective than acid pretreatment at same processing conditions for grass and hardwood. The ethanol-isopropanol mixture, and glycerol with 0.4% (w/v) sodium hydroxide were the promising organic solvent systems for the pretreatment of corn stover (grass), and poplar (hardwood), respectively. None of the pretreatment methods used in this study worked well for Douglas fir (softwood), which indicates a need to further optimize appropriate processing conditions, better solvent and catalyst for effective pretreatment of this biomass. The brown midrib (bmr) mutations improved the biomass quality as a feedstock for biochemicals production in some sorghum cultivars and bmr types, while adverse effects were observed in others. These results indicated that each potential sorghum cultivar should be separately evaluated for each type of bmr mutation to develop the best sorghum line as an energy crop. Development of an appropriate biomass processing technology to generate separate cellulose and hemicellulose hydrolyzates is required for efficient 2,3-butanediol (BD) fermentation using a non-pathogenic bacterial strain, Bacillus licheniformis DSM 8785. This culture is significantly more efficient for BD fermentation in single sugar media than Klebsiella oxytoca ATCC 8724. Though K. oxytoca is a better culture reported so far for BD fermentation from diverse sugars media, but it is a biosafety level 2 organism, which limits its commercial potential.

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Nessa pesquisa foram testados separadamente dois inóculos solo/compostagem e lodo termofílico de reator anaeróbio de manta de lodo e fluxo ascendente (UASB) do tratamento de vinhaça em relação ao potencial de produção de compostos de valor agregado a partir do bagaço de cana-de-açúcar (BCA) em reatores em batelada em condição mesofílica e termofílica, respectivamente. Pré-tratamentos térmico, ácido e diluição seriada foram aplicados ao inóculo termofílico, como tentativa de inibir as arqueias metanogênicas. A diluição seriada foi o pré-tratamento aplicado em ambos os inóculos, mesofílico e termofílico, para obtenção de consórcio de bactérias fermentadoras. Cinco meios de culturas foram testados como fonte de nutrientes para o crescimento de bactérias celulolíticas e fermentadoras. Dentre esses foi selecionado para os ensaios mesofílicos e termofílicos, o meio de cultura mais complexo suplementado com extrato de levedura. O BCA foi submetido à pré-tratamento biológico, térmico, explosão a vapor, deslignificação alcalina e hidrotérmico sendo o último utilizado nos ensaios do planejamento fatorial. O efeito das variáveis independentes de concentração de extrato de levedura e temperatura foi avaliado na produção de hidrogênio, metano e ácidos orgânicos a partir do inóculo termofílico. O efeito da concentração de extrato de levedura e substrato (BCA) foi avaliado na produção de bioprodutos a partir do inóculo mesofílico (37ºC). A maior produção de hidrogênio foi de 17,30 mmol/L à 60ºC e 3,42 g/L de extrato de levedura para a condição termofílica. Em relação aos ensaios mesofílicos observou-se 1,53 mmol/L com 3,42 e 5,00 g/L de extrato de levedura e BCA, respectivamente. Caracterização taxonômica e funcional dos microrganismos dos reatores de melhor desempenho de produção de hidrogênio dos planejamentos fatoriais termofílico e mesofílico foi realizada por análise Metagenômica (Illumina HiSeq). Nestas condições foram identificados microrganismos dos domínios Archaea, Bacteria, Eukarya, além de vírus. Para o domínio Bacteria foram identificados microrganismos celulolíticos e fermentadores como Coprothermobacter e Clostridium, enquanto para o domínio Archaea, foram identificadas metanogênicas hidrogenotróficas e acetoclásticas, como Methanothermobacter e Methanosarcina. Foram ainda identificados genes codificantes de enzimas catalisadoras da degradação de celulose, hemicelulose e lignina, constituintes principais da biomassa lignocelulósica utilizada como substrato, tais como celulase, carboxylesterase e 2-ácido hidroxi oxidase, respectivamente. Microrganismos aderidos no BCA in natura foram observados por microscopia eletrônica de varredura (MEV) e identificados por sequenciamento do RNAr 16S, e semelhantes a Streptomyces, Paenibacillus, Stenotrophomonas, Sphingomonas. Os microrganismos do lodo termofílico, solo e compostagem foram caracterizados por sequenciamento do RNAr 16S, e foram semelhantes a Clostridium, Thermoanaerobacter, Caloramator, Anaerobaculum, Tatlockia, Coprothermobacter, Dysgonomonas, Coprococcus, Sporomusa, Methanobacterium, Methanothermobacter, Methanosaeta, dentre outros. / In the present study, two inoculum (soil/compost and thermophilic sludge from upflow anaerobic sludge blanket from vinasse treatment) were separately evaluated as potential to production of value-added products from sugarcane bagasse in mesophilic and thermophilic conditions, respectively. Thermal, acid and serial dilution pretreatments were performed in the thermophilic inoculum to inhibition of methanogenic archaea. Serial dilution was applied into the mesophilic inoculm. Five culture medium were evaluated as nutritional source to enrichment of cellulolytic and fermenters bacteria; between then, the most complex one, supplemented with yeast extract was selected for the mesophilic and thermophilic bioassays. The sugarcane bagasse (SCB) was submitted to biological, thermal, stem explosion alkaline delignification and hydrothermal pretreatments, and the last one was used as substrate for the factorial designs. The effect of independent variables, such as yeast extract and temperature were evaluated on the hydrogen, methane and organic acids production from the thermophilic inoculum. The effect of yeast extract and substrate (SCB) concentrations were evaluated on the bioproducts generation from the mesophilic inoculum. The highest hydrogen production of 17.3 mmol/L was obtained at 60ºC and 3.42 g/L of yeast extract, on the thermophilic factorial design. In relation to the mesophilic factorial design, obtained 1.53 mmol/L of hydrogen with 3.42 and 5.00 g/L of yeast extract and SCB, respectively. Taxonomical and functional characterizations from the microorganisms were performed in the reactors with highest hydrogen production on the factorial designs using Metagenomics analysis (Illumina HiSeq). In both condition, mesophilic and thermophilic were found microorganisms from Archaea, Bacteria, Eukarya domin, besides Viruses. Concerning the Bacteria domain were found cellulolytic and fermenters microorganisms similar to Coprothermobacter and Clostridium, whiles for Archaea domain were identified hydrogenotrophic and acetoclastic methanogenic similar to Methanothermobacter and Methanosarcina. There were obtained genes coding to enzymes related to the cellulose, hemicellulose and lignin degradation such as carboxylesterase e 2-acid-hydroxioxidase, respectively. Microorganisms adhered into the in natura SCB fiber were observed by scanning electronic microscopy (SEM) and identified by 16 S rRNA sequencing, mainly as similar to Streptomyces, Paenibacillus, Stenotrophomonas, Sphingomonas. The microorganisms from the thermophilic sludge, soil and composting were also characterized by 16S RNAr sequencing and were similar to Clostridium, Thermoanaerobacter, Caloramator, Anaerobaculum, Tatlockia, Coprothermobacter, Dysgonomonas, Coprococcus, Sporomusa, Methanobacterium, Methanothermobacter, Methanosaeta, among others.

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Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-10-06T10:55:44Z No. of bitstreams: 2 Dissertação - Aline Rodrigues Gama - 2016.pdf: 2281415 bytes, checksum: a79af0203dd2a1cfd381c59e3e9d6d7b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-10-06T11:22:35Z (GMT) No. of bitstreams: 2 Dissertação - Aline Rodrigues Gama - 2016.pdf: 2281415 bytes, checksum: a79af0203dd2a1cfd381c59e3e9d6d7b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-10-06T11:22:35Z (GMT). No. of bitstreams: 2 Dissertação - Aline Rodrigues Gama - 2016.pdf: 2281415 bytes, checksum: a79af0203dd2a1cfd381c59e3e9d6d7b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-09-14 / The use of carbohydrates derived from agricultural waste is important in the industry of food, textiles, paper, detergents, animal feed and in the production of bioethanol. Some filamentous bacteria are used in the enzymatic degradation processes, such as Streptomyces thermocerradoensis I3, which was isolated from soil and this work was selected for the production of cellulases and xylanases by growing in semi-solid fermentation (SSF) in medium supplemented with wheat bran (WB) as carbon source. S. thermocerradoensis I3 it was maintained for 4 days at 37 ° C and showed a higher production of Endoglucanase (2,92 U/mL) and Xylanase (12,34 U/mL) after 72 hours of cultivation and β-glucosidase (0,023 U/mL) and FPase (2,82 U/mL) after 96 hours of cultivation. The 96-hour extract was concentrated. The enzyme present in the concentrated extract presented molecular mass of 17 kDa. It showed activity for cellulase and xylanases confirmed by zimograms and enzymatic activities. The crude extract (EB) and the concentrated extract (EC) were analyzed for pH and temperature optima for activity of cellulases and xylanases. The results showed that the highest activity of the total cellulase (FPase) was at pH 6.0 at 60 °C (EB) and pH in the range 3.0 to 6.0 at 80 °C (EC); the endoglucanase has higher activity at pH 6.0 at 55 °C (EB and EC); xylanase showed higher activity at pH 8.0 at 70 °C (EB and EC). The xylanase activity of EB and EC showed thermostability 60% after 2 hours of incubation at 60 °C and the endoglucanase activity of EB and EC remained above 50% after 4 hours of incubation at 50 °C, 60 °C and 70 °C. Qualitative analysis observed by TLC (Thin layer chromatography) showed the production of oligosaccharides and xilooligômeros from the hydrolysis of different substrates. S. thermocerradoensis I3 successfully used the WB in SSF producing enzymes that have the characteristics necessary for their industrial application. / A utilização de carboidratos oriundos dos resíduos agrícolas faz-se importante nas indústrias de alimentos, tecidos, papeis, detergentes, ração animal e ainda na produção de bioetanol. Algumas bactérias filamentosas são utilizadas nos processos de hidrólise enzimática, como Streptomyces thermocerradoensis I3, o qual foi isolado do solo e, neste trabalho, selecionado para produção de celulases e xilanases através de cultivo em fermentação semi-sólida (FSS) em Meio Mínimo suplementado com farelo de trigo (FT) como fonte de carbono. S. thermocerradoensis I3 foi cultivado por 4 dias à 37 °C e apresentou maior produção de Endoglucanase (2,92 U/mL) e Xilanase (12,34 U/mL) após 72 horas de cultivo e de β-glicosidase (0,023 U/mL) e FPase (2,82 U/mL) após 96 horas de cultivo. O extrato de 96 horas foi concentrado e a enzima presente no extrato concentrado apresentou Massa Molecular de 17 kDa. Ela apresentou atividade de celulase e xilanase, as quais foram confirmadas por zimogramas e determinação das atividades enzimáticas. O extrato bruto (EB) e o extrato concentrado (EC) foram analisados quanto ao pH e temperatura ótimos para a atividade de celulases e xilanase. Os resultados obtidos demonstraram que a maior atividade de celulases totais (FPase) foi em pH 6,0 à 60 °C (EB) e pH na faixa de 3,0 e 6,0 à 80 °C (EC); a enduglucanase apresentou maior atividade na faixa de pH 6,0 à 55 °C (EB e EC); a xilanase apresentou maior atividade em pH 8,0 à 70 °C (EB e EC). A atividade de xilanase do EB e da EC apresentou termoestabilidade de 60% após 2 horas de incubação à 60 °C e a atividade de endoglucanase do EB e do EC permaneceu acima de 50% após 4 horas de incubação à 50, 60 e 70 °C. As análises qualitativas observadas por TLC (Thin Layer Chromatography) revelaram a liberação de oligossacarídeos e xilooligômeros a partir da hidrólise de diferentes substratos. S. thermocerradoensis I3 utilizou com sucesso o FT em FSS produzindo enzimas que apresentam as características necessárias para sua aplicação industrial.

A biomassa lignocelulósica é uma alternativa atrativa para o aumento na oferta de biocombustíveis, uma vez que é constituída de celulose e hemicelulose. Esses polímeros são constituídos principalmente de unidades menores de glicose e xilose, os quais por meio de bactérias anaeróbias termófilas, podem ser metabolizados em etanol. Portanto, estabeleceu-se o objetivo desse trabalho, em utilizar as principais fontes de carbono da biomassa lignocelulósica (celulose, glicose e xilose), e produzir etanol por meio da ação de consórcio microbiano selecionado a partir de inóculo termófilo e anaeróbio. O inóculo foi submetido a condição de crescimento com variação de pH (2,3,4,5,6,e 7) e variação de dois meios de cultivo em reatores em batelada, visando favorecer bactérias celulolíticas e fermentativas produtoras de etanol. Para a produção de etanol, o pH e meio de cultivo mais adequados foram 7,0 e Meio Thermoanaerobacter ethanolicus, respectivamente. A partir do inóculo enriquecido nas condições nutricionais de pH e meio de cultivo, prosseguiu-se a realização dos ensaios de produção de etanol a partir de celulose, glicose e xilose (1g/L de cada substrato), em pH 7 e meio T. ethanolicus. Os ensaios foram realizados em reator em batelada, em triplicata, a 55 ºC, ambos seguidos de um reator controle, sem adição desses substratos orgânicos. Os rendimentos de etanol foram de 1,73 mol etanol/mol glicose e 1,33 mol de etanol /mol de xilose. Para o substrato celulose obteve-se 1,88 mmol de etanol/g de celulose. Para os reatores controle de glicose, celulose e xilose, no qual o extrato de levedura foi a única fonte orgânica adicionada, a produção de etanol foi 1,27 mmol/L, 0,39 mmol/L e 1,65 mmol/L, respectivamente. Em todos os reatores foi detectado produção de ácido acético, ácido butírico e ácido propiônico. A produção de ácido acético foi de 5,73 mmol/L, 9,73 mmol/L e 14,45 mmol/L, para os reatores de glicose, celulose e xilose, respectivamente. No reator com glicose, observou-se baixo rendimento de hidrogênio (0,31 mol hidrogênio/mol glicose), e nos demais reatores não foi constatado produção desse gás. Em contrapartida, observou-se rendimentos de 6,6 mmol de metano/g de celulose e 0,68 mol de metano/mol de xilose para os respectivos reatores. Dessa forma, pode-se mencionar que em função das características do consórcio microbiano foi possível obter a degradação da celulose e metabolização da glicose e xilose em etanol. / Lignocellulosic biomass is an attractive alternative to increase biofuels proposal, as its composed of cellulose and hemicellulose. These polymers are consisted in individual molecules of glucose and xylose, through some thermophilic bacteria, can metabolize these carbohydrates in ethanol. Therefore, this study reports on using the principals carbon sources of lignocellulosic biomass (cellulose, glucose, and xylose), and producing ethanol through microbial consortium from anaerobic and thermophilic inoculum. The biomass was submitted to variation of pH (2,3,4,5,6, and 7) and two kinds of medium, due to ethanol production in batch reactors. For ethanol production, the optimized pH and medium were 7,0 and Thermoanaerobacter ethanolicus medium, respectively. The enriched culture was being cultivated in pH and medium experiments were used to ethanol production experiments that carried out in batch reactors, from cellulose, glucose and xylose were realized in triplicate and were maintained at 55 °C, in both batches had a control reactor (without these organics substrates). Positive results in ethanol yields were 1,73 mol ethanol/ mol glucose and 1,33 mol ethanol/ mol xylose. In celluloses reactors the microbial consortium was efficient in substrate degradation, however, was obtained lower ethanol yields (1,88 mol ethanol/ g cellulose). In control reactors from glucose, cellulose and xylose, that yeast extract was the unique organic source, ethanol production was 1,27 mmol/L, 0,39 mmol/L e 1,65 mmol/L, respectively. In all reactors were detected acetic, butyric and propionic acids. The acetic acid production was 5,73 mmol/L, 9,73 mmol/L e 14,45 mmol/L in glucose, cellulose and xylose reactors, respectively. For glucoses reactors were observed lower hydrogen production (0,31 mol hydrogen/ mol glucose), in the other reactors did not observed gases production. Instead of the following yields were obtained: 6,6 mmol methane/ g cellulose and 0,68 mol methane/ mol xylose. Taking this into account, microbial consortium enriched had characteristics to degrade cellulose and metabolize glucose and xylose to ethanol.

Magister Scientiae - MSc / Lignocellulosic biomass represents an important renewable resource for biofuels production. Lignocellulosic biomass is comprised of cellulose, hemicellulose and lignin. Lignocellulosics are highly recalcitrant to enzymatic degradation and due to its complex nature a range of enzymes are required to synergistically hydrolyse biomass. Many microorganisms are capable of producing these enzymes as part of their hemicellulolytic hydrolysis system(s). The aim of this study was the characterisation of a thermophilic actinobacterial isolate (ORS10), capable of producing hemicellulosic enzymes, and the cloning and characterization of a hemicellulosic enzyme produced by the isolate. Phylogenetic analyses clustered ORS10 with species of the genus Streptomyces. BLAST analysis revealed that ORS10 was most closely related to Streptomyces achromogenes (99% identity). A small-insert genomic library was constructed and a putative acetylxylan esterase (AXEase) gene, axe10, was identified. The enzyme, Axe10, has moderate similarity to α/β hydrolase proteins, and contains an esterase/lipase superfamily conserved domain and a typical AXEase catalytic triad. The axe10 gene was sub-cloned into an expression vector [pET21a(+)] and a 28.7 kDa protein with demonstrated AXE activity was purified from E. coli Rosetta (DE3) pLysS. Axe10 displayed optimum activity at 37oC and pH 7.0. Despite being derived from a thermophilic Streptomyces species Axe10 was not thermostable. However, given the relative novelty of Axe10, further characterisation and assessment of this enzyme is warranted. / South Africa

Thesis (M.Sc. (Microbiology)) -- University of Limpopo, 2020 / Production of bioethanol from lignocellulosic biomass has gained significant attention worldwide as an alternative fuel source for the transportation sector without affecting food supply. Efficient conversion of pentose sugars (L-arabinose and D-xylose) produced during hydrolysis of hemicellulose to ethanol can enhance the economic viability. In this study, a total of 390 yeasts isolated from Marula wine, the gut of dung beetles, herbal concoctions and banana residues were screened for the ability to ferment L-arabinose and D-xylose. Fourteen yeasts were able to ferment both pentose sugars and ten strains were subjected to an adaptation process in the presence of acetic acid using L-arabinose as carbon source. Four adapted strains of Meyerozyma caribbica were able to ferment L-arabinose to ethanol and arabitol in the presence of 3 g/L acetic acid at 35 °C. Meyerozyma caribbica Mu 2.2f fermented D-xylose, L-arabinose and a mixture of D-xylose and L-arabinose to produce 1.7, 3.0 and 1.9 g/L ethanol, respectively, compared to the parental strain with 1.5, 1.0 and 1.8 g/L ethanol, respectively, in the absence of acetic acid. The adapted strain of M. caribbica Mu 2.2f produced 3.6 and 0.8 g/L ethanol from L-arabinose and D-xylose, respectively in the presence of acetic acid while the parental strain failed to grow. In the bioreactor, the adapted strain of M. caribbica Mu 2.2f produced 5.7 g/L ethanol in the presence of 3 g/L acetic acid with an ethanol yield and productivity of 0.338 g/g and 0.158 g/L/h, respectively at a KLa value of 3.3 h-1. The adapted strain produced 26.7 g/L arabitol with a yield of 0.900 g/g at a KLa value of 4.9 h-1. Meyerozyma caribbica Mu 2.2f could potentially be used to produce ethanol and arabitol under stressed conditions. / National Research Foundation (NRF)