BackgroundThe organic acid producer Aspergillus oryzae and Rhizopus delemar are able to convert several alternative carbon sources to malic and fumaric acid. Thus, carbohydrate hydrolysates from lignocellulose separation are likely suitable as substrate for organic acid production with these fungi.ResultsBefore lignocellulose hydrolysate fractions were tested as substrates, experiments with several mono- and disaccharides, possibly present in pretreated biomass, were conducted for their suitability for malic acid production with A. oryzae. This includes levoglucosan, glucose, galactose, mannose, arabinose, xylose, ribose, and cellobiose as well as cheap and easy available sugars, e.g., fructose and maltose. A. oryzae is able to convert every sugar investigated to malate, albeit with different yields. Based on the promising results from the pure sugar conversion experiments, fractions of the organosolv process from beechwood (Fagus sylvatica) and Miscanthus giganteus were further analyzed as carbon source for cultivation and fermentation with A. oryzae for malic acid and R. delemar for fumaric acid production. The highest malic acid concentration of 37.9 ± 2.6 g/L could be reached using beechwood cellulose fraction as carbon source in bioreactor fermentation with A. oryzae and 16.2 ± 0.2 g/L fumaric acid with R. delemar.ConclusionsWe showed in this study that the range of convertible sugars for A. oryzae is even higher than known before. We approved the suitability of fiber/cellulose hydrolysate obtained from the organosolv process as carbon source for A. oryzae in shake flasks as well as in a small-scale bioreactor. The more challenging hemicellulose fraction of F. sylvatica was also positively evaluated for malic acid production with A. oryzae.

Background The co-production of single cell oil (SCO) with value-added products could improve the economic viability of industrial SCO production. The newly isolated oleaginous yeast Cryptococcus podzolicus DSM 27192 was able to co-produce SCO intracellularly and gluconic acid (GA) extracellularly. In this study, the metabolic regulation of carbon distribution between SCO and GA through process optimization was comprehensively investigated. Results The carbon flow distribution between SCO and GA was significantly influenced by the cultivation conditions, such as nitrogen sources, glucose concentration and dissolved oxygen concentration. It was found that organic nitrogen sources were beneficial for SCO accumulation, while GA production was decreased. Dissolved oxygen concentration (DOC) was found to enhance SCO accumulation, while high glucose concentration was more favorable for GA accumulation. Hence, a two-stage DOC or glucose concentration-controlled strategy was designed to improve cell growth and direct carbon distribution between SCO and GA. Moreover, C. podzolicus DSM 27192 could degrade its stored lipids to synthesize GA in the late stationary phase, although considerable amounts of glucose remained unconsumed in the culture medium, indicating the importance of fermentation time control in co-production systems. All these observations provide opportunity to favor either the production of SCO or GA or rather their simultaneous production. Conclusions Co-production of SCO and GA by C. podzolicus DSM 27192 can improve the economical value for microbial lipid-derived biodiesel production. Moreover, the results of the proposed co-production strategy might give guidance for other co-production systems.

Evaluation of SCO Downstream Processing At disruption efficiencies of >90%, lipids can be extracted at high yields, whereas at lower cell disruption efficiencies, considerable amounts of lipids will not be accessible for extraction regardless of the solvents used. Furthermore, it was shown that hexaneethanol which is commonly used for extraction of algal lipids is also highly efficient for yeasts.

Trichosporonaceae incorporates six genera of physiologically and ecologically diverse fungi including both human pathogenic taxa as well as yeasts of biotechnological interest, especially those oleagenic taxa that accumulate large amounts of single cell oils (Scos). Here, we have undertaken comparative genomic analysis of thirty-three members of the family with a view to gain insight into the molecular determinants underlying their lifestyles and niche specializations. phylogenomic analysis revealed potential misidentification of three strains which could impact subsequent analyses. Evaluation of the predicted proteins coding sequences showed that the free-living members of the family harbour greater numbers of carbohydrate active enzymes (cAZYmes), metallo-and serine peptidases compared to their host-associated counterparts. phylogenies of selected lipid biosynthetic enzymes encoded in the genomes of the studied strains revealed disparate evolutionary histories for some proteins inconsistent with the core genome phylogeny. However, the documented oleagenic members distinctly cluster based on the constitution of the upstream regulatory regions of genes encoding acetyl-coA carboxylase (Acc), Atp-citrate synthase (AcS) and isocitrate dehydrogenase [nADp] (icDH), which are among the major proteins in the lipid biosynthetic pathway of these yeasts, suggesting a possible pattern in the regulation of these genes. The basidiomycetous fungal family Trichosporonaceae belongs to the order Trichosporonales, the class Tremellomycetes, and subphylum Agaricomycotina and incorporates morphologically and physiologically diverse, aromatic compound-assimilating yeasts 1. Recently the taxonomy of this family was revised to include six genera, namely Apiotrichum, Cutaneotrichosporon, Effuseotrichosporon, Haglerozyma, Trichosporon (type genus) and Vanrija. This revision was based on phylogenetic analysis of seven markers, namely LSU (D1/D2 domains) and SSU rRNA, the Internal Transcribed Spacer (ITS) and the protein coding genes RPB1, RPB2, TEF1 and CYTB and a combination of morphological, biochemical and physiological characteristics 1,2. Members of the Trichosporonaceae show a global distribution and have been recovered from a wide range of environments. Cutaneotrichosporon spp. are most frequently associated with a human host, and may represent opportunistic human pathogens. Trichosporon spp. form part of the natural microflora on human and animal skin and result in a non-serious mycosis of hair termed white piedra 3. However, they have also been implicated in trichosporonosis, a collection of opportunistic infections caused by a number of species, including Trichosporon asahii, T. asteroides and T. ovoides 4. By contrast Apiotrichum and Vanrija spp. are generally free-living and have been isolated from water bodies, food sources and rotten wood (Table 1). While the Trichosporonaceae include several opportunistic human pathogens, there has also been increased interest in these taxa for a broad range of biotechnological applications...

Background Biotechnologically produced microbial lipids are of interest as potential alternatives for crude and plant oils. Their lipid profile is similar to plant oils and can therefore be a substitute for the production of biofuels, additives for food and cosmetics industry as well as building blocks for oleochemicals. Commercial microbial lipids production, however, is still not profitable and research on process optimization and cost reduction is required. This study reports on the process optimization using glucose or xylose with the unconventional oleaginous yeast Saitozyma podzolica DSM 27192 aiming to reduce the applied carbon source amount without sacrificing lipid productivity. Results By optimizing the process parameters temperature and pH, lipid productivity was enhanced by 40%. Thereupon, by establishing a two-phase strategy with an initial batch phase and a subsequent fed-batch phase for lipid production in which a constant sugar concentration of about 10 g/L was maintained, resulted in saving of ~ 41% of total glucose and ~ 26% of total xylose. By performing the automated continuous sugar feed the total sugar uptake was improved to ~ 91% for glucose and ~ 92% for xylose and thus, prevented waste of unused carbon source in the cultivation medium. In addition, reduced glucose cultivation resulted in to 28% higher cell growth and 19% increase of lipid titer. By using xylose, the by-product xylonic acid was identified for the first time as by-product of S. podzolica. Conclusions These findings provide a broad view of different cultivation process strategies with subsequent comparison and evaluation for lipid production with S. podzolica. Additionally, new biotechnological characteristics of this yeast were highlighted regarding the ability to produce valuable organic acids from sustainable and renewable sugars.

We report here the draft genome of Saitozyma podzolica DSM 27192 sequenced based on PacBio chemistry. This yeast isolate produces large amounts of single-cell oil (SCO) and gluconic acid (GA).

Here, we present the draft genome sequence of Apiotrichum porosum DSM 27194 generated on PacBio platform. Characterization of this oleaginous yeast originally collected from the grassland in Karlsruhe Germany, revealed potential for its utilization as a source of single cell oil (SCO) and gluconic acid (GA). The availability of the genome sequence provides a valuable resource for the elucidation of the genetic processes determining SCO and GA biosynthesis.

Glycolipids are non-ionic surfactants occurring in numerous products of daily life. Due to their surface-activity, emulsifying properties, and foaming abilities, they can be applied in food, cosmetics, and pharmaceuticals. Enzymatic synthesis of glycolipids based on carbohydrates and free fatty acids or esters is often catalyzed using certain acyltransferases in reaction media of low water activity, e.g., organic solvents or notably Deep Eutectic Systems (DESs). Existing reports describing integrated processes for glycolipid production from renewables use many reaction steps, therefore this study aims at simplifying the procedure. By using microwave dielectric heating, DESs preparation was first accelerated considerably. A comparative study revealed a preparation time on average 16-fold faster than the conventional heating method in an incubator. Furthermore, lipids from robust oleaginous yeast biomass were successfully extracted up to 70% without using the pre-treatment method for cell disruption, limiting logically the energy input necessary for such process. Acidified DESs consisting of either xylitol or sorbitol and choline chloride mediated the one-pot process, allowing subsequent conversion of the lipids into mono-acylated palmitate, oleate, linoleate, and stearate sugar alcohol esters. Thus, we show strong evidence that addition of immobilized Candida antarctica Lipase B (Novozym 435®), in acidified DES mixture, enables a simplified and fast glycolipid synthesis using directly oleaginous yeast biomass.