Volkmar Passoth

• PhD
• Professor at Swedish University of Agricultural Sciences

Cassava is an important staple food that contributes to the food security of small-scale Mozambican farmers. In southern Mozambique, cassava roots are usually processed into cassava roasted flour, locally known as “rale”. The handling and processing practices connected to “rale” production may introduce microbial contamination. We assessed the micr...

Background We conducted extractions using supercritical carbon dioxide (SC-CO 2 ) and conventional solvent methods to extract lipids and carotenoids from R. toruloides CBS 14 cells grown on wheat straw hydrolysate. The lipid extracts were analyzed using gas chromatography (GC), and the carotenoids were identified and quantified using ultra-high per...

Tempeh is a fermented soybean food with high nutritional value, culinary versatility, and palatability. Its popularity is rising because it aligns with the trend towards sustainable and healthy plant-based diets. However, consumers have exhibited a strong preference for local ingredients over soy. Faba bean is a promising raw material in Scandinavi...

The project MUSA MUshrooms for Sustainable Agriculture is an effort to use mushroom-based processes to enhance agriculture sustainability in Nordic and Baltic countries. The project covers both the production of fruitbodies of edible fungi and the upgrading of the exhausted substrate from mushroom cultivation. The suitability of residues generated...

Background Aquaculture is a major user of plant-derived feed ingredients, such as vegetable oil. Production of vegetable oil and protein is generally more energy-intensive than production of the marine ingredients they replace, so increasing inclusion of vegetable ingredients increases the energy demand of the feed. Microbial oils, such as yeast oi...

Carboxylic acids have become interesting platform molecules in the last years due to their versatility to act as carbon sources for different microorganisms or as precursors for the chemical industry. Among carboxylic acids, short-chain fatty acids (SCFAs) such as acetic, propionic, butyric, valeric, and caproic acids can be biotechnologically prod...

Background Lipid formation from glycerol was previously found to be activated in Rhodotorula toruloides when the yeast was cultivated in a mixture of crude glycerol (CG) and hemicellulose hydrolysate (CGHH) compared to CG as the only carbon source. RNA samples from R. toruloides CBS14 cell cultures grown on either CG or CGHH were collected at diffe...

Microbial lipids produced from lignocellulose and crude glycerol (CG) can serve as sustainable alternatives to vegetable oils, which production is in many cases accompanied with monocultures, land use changes, or rain forest clearings. Our projects aim to understand the physiology of microbial lipid production by oleaginous yeasts, optimise the pro...

Background Lipid formation from glycerol was previously found to be activated in Rhodotorula toruloides when the yeast was cultivated in a mixture of crude glycerol (CG) and hemicellulose hydrolysate (CGHH) compared to CG as the only carbon source. RNA samples from R. toruloides CBS14 cell cultures grown on either CG or CGHH were collected at diffe...

Bioenergy will be one of the most important renewable energy sources in the conversion from fossil fuels to bio‐based products. Short‐rotation‐coppice Salix could be a key player in this conversion since Salix has rapid growth, positive energy balance, an easy to manage cultivation system with vegetative propagation of plant material and multiple h...

Production of carotenoids and lipids by Rhodotorula toruloides CBS 14 cultivated on wheat straw hydrolysate was investigated. An ultra-high-performance liquid chromatography (UHPLC) method for carotenoid quantification was developed and validated. Saponification effects on individual carotenoid quantification were identified, and lipid and caroteno...

The genus Rhodotorula includes basidiomycetous oleaginous yeast species. Rhodotorula babjevae can produce compounds of biotechnological interest such as lipids, carotenoids, and bio- surfactants from low value substrates such as lignocellulose hydrolysate. High-quality genome assemblies are needed to develop genetic tools and to understand fungal e...

The genus Rhodotorula includes basidiomycetous oleaginous yeast species. R. babjevae can produce compounds of biotechnological interest such as lipids, carotenoids and biosurfactants from low value substrates such as lignocellulose hydrolysate. High-quality genome assemblies are needed to develop genetic tools and to understand fungal evolution and...

Diets low in fermentable oligo-, di-, and monosaccharides and polyols (FODMAPs) can help reduce symptoms in 50 to 80% of patients suffering from irritable bowel syndrome. Patients are, therefore, often advised to avoid products contributing to FODMAP intake, such as cereal grain products. However, these products are nutritious staple foods and avoi...

Rhodotorula toruloides is an oleaginous yeast with high biotechnological potential. In order to understand the molecular physiology of lipid synthesis in Rhodosporidium toruloides and to advance metabolic engineering, a high-resolution genome is required. We constructed a genome draft of R. toruloides CBS 14, using a hybrid assembly approach, consi...

Strains of the yeast genus Blastobotrys (subphylum Saccharomycotina) represent a valuable biotechnological resource for basic biochemistry research, single-cell protein, and heterologous protein production processes. Species of this genus are dimorphic, non-pathogenic, thermotolerant, and can assimilate a variety of hydrophilic and hydrophobic subs...

Background Microbial oils, generated from lignocellulosic material, have great potential as renewable and sustainable alternatives to fossil-based fuels and chemicals. By unravelling the diversity of lipid accumulation physiology in different oleaginous yeasts grown on the various carbon sources present in lignocellulose hydrolysate (LH), new targe...

Rhodotorula toruloides is an oleaginous yeast with high biotechnological potential. In order to understand the molecular physiology of lipid synthesis in R. toruloides and to advance metabolic engineering, a high-resolution genome is required. We constructed a genome draft of R. toruloides CBS 14, using a hybrid assembly approach, consisting of sho...

Background Crude glycerol (CG) and hemicellulose hydrolysate (HH) are low—value side-products of biodiesel transesterification and pulp—and paper industry or lignocellulosic ethanol production, respectively, which can be converted to microbial lipids by oleaginous yeasts. This study aimed to test the ability of oleaginous yeasts to utilise CG and H...

Background: Crude glycerol (CG) and hemicellulose hydrolysate (HH) are low- value side-products of biodiesel transesterification and pulp- and paper industry, respectively, which can be converted to microbial lipids by oleaginous yeasts. This study aimed to test the ability of oleaginous yeasts to utilise CG and HH and mixtures of them as carbon so...

The production of microbial protein in the form of yeast grown on lignocellulosic sugars and nitrogen-rich industrial residues is an attractive approach for reducing dependency on animal and plant protein. Growth media composed of enzymatically saccharified sulfite-pulped spruce wood, enzymatic hydrolysates of poultry by-products and urea were used...

Background: A possible future shortage of feed protein will force mankind to explore alternative protein sources that can replace conventional soymeal or fishmeal. Several large industrial organic side-streams could potentially be upgraded to feed protein using a fermentation process to generate single cell protein. Yeast is the most widely accept...

Amid known microbial bioethanol producers, the yeast Scheffersomyces (Pichia) stipitis is particularly promising in terms of alcoholic fermentation of both glucose and xylose, the main constituents of lignocellulosic biomass hydrolysates. However, the ethanol yield and productivity, especially from xylose, are still insufficient to meet the require...

Brettanomyces naardenensis is a spoilage yeast with potential for biotechnological applications for production of innovative beverages with low alcohol content and high attenuation degree. Here, we present the first annotated genome of B. naardenensis CBS 7540. The genome of B. naardenensis CBS 7540 was assembled into 76 contigs, totaling 11,283,07...

In a 10‐week study, we evaluated the effects of replacing 20%, 40% or 60% of fish‐ meal (present in control diet at 300 g/kg) on a digestible protein basis with yeast Saccharomyces cerevisiae or a yeast mixture of Wickerhamomyces anomalus and S. cer‐ evisiae on growth performance, nutrient digestibility, nutrient retention and intestinal health of...

Biogas plants serve as hubs for the collection and utilization of highly nutritious waste streams from households and agriculture. However, their outputs (biogas and digestate) are of relatively low economic value. Here, we explore the co-production of yeast single cell protein, a potentially valuable feed ingredient for aquaculture and other anima...

Straw is an agricultural residue of the production of e.g. cereals, rapeseed or sunflowers. It includes dried stalks, leaves, and empty ears and corncobs, which are separated from the grains during harvest. Straw is a promising lignocellulosic feedstock with a beneficial greenhouse gas balance for the production of biofuels and chemicals. Like all...

Background: Lipid extraction for quantification of fat content in oleaginous yeasts often requires strong acids and harmful organic solvents; it is laborious and time-consuming. Therefore, in most cases just endpoint measurements of lipid accumulation are performed and kinetics of intracellular lipid accumulation is difficult to follow. To address...

Background: Oleaginous yeasts are considered as a potential lipid source for food, feed and biofuel production. In order to make the yeast-based lipid production environmentally and economically sustainable, there is a need for screening studies in order to find the best yeast lipid producers on different substrates, and to optimize cultivation co...

Here, we present the genome of the industrial ethanol production strain Brettanomyces bruxellensis CBS 11270. The nuclear genome was found to be diploid, containing four chromosomes with sizes of ranging from 2.2 to 4.0 Mbp. A 75 Kbp mitochondrial genome was also identified. Comparing the homologous chromosomes, we detected that 0.32% of nucleotide...

Variants in CBS 11270. (TXT)

List of genes without variants in CBS 11270. (TXT)

Copy number variation in CBS 11270. (TXT)

List of genes with reduced coverage. (TXT)

Characterization of repeats in CBS 11270. (TXT)

Characterization of variants in CBS 2499. (TXT)

Clustering of genes with reduced coverage in CBS 11270. (DOCX)

Haplotype sampling of CBS 11270. (DOCX)

Distribution of SNPs per Kbp gene. (DOCX)

Variation in coverage of chromosomes in CBS 11270. (DOCX)

Characterization of variants in CBS 11270. (TXT)

List of genes in CBS 11270 with variants. (TXT)

List of genes in CBS 2499 with variants. (TXT)

List of genes without variants in CBS 2499. (TXT)

List of genes present in CBS 11270 but not in CBS 2499. (DOCX)

Variants in CBS 2499. (TXT)

Distribution of genes with different numbers of variants in heterozygous sites in the genome of CBS 11270 and between genomes of CBS 11270 and CBS 2499. (DOCX)

Position of centromeres. (DOCX)

List of genes present in CBS 2499 but not in CBS 11270. (DOCX)

Enset (Ensete ventricosum) is the basis of the staple food consumed by about 20% of the Ethiopian population. Kocho is one of the food products generated from enset by spontaneous fermentation of decorticated and pulverized pseudostem and corm sections. We isolated culturable microbes associated with kocho from different stages of fermentation. Twe...

Yeasts can be used to convert organic food wastes to protein-rich animal feed in order to recapture nutrients. However, the reuse of animal-derived waste poses a risk for the transmission of infectious prions that can cause neurodegeneration and fatality in humans and animals. The aim of this study was to investigate the ability of yeasts to reduce...

This study investigates the replacement of vegetable oil (VO) in aquaculture feed for Arctic char (Salvelinus alpinus) with oil produced by the oleaginous yeast Lipomyces starkeyi grown in lignocellulose (wheat straw) hydrolysate. VO is extensively used to partially replace fish oil in aquaculture feed, which can be seen as non-sustainable. VO itse...

This study investigates biofuel production from wheat straw hydrolysate, from which furfural was extracted using a patented method developed at the Latvian State Institute of Wood Chemistry. The solid remainder after furfural extraction, corresponding to 67.6% of the wheat straw dry matter, contained 69.9% cellulose of which 4% was decomposed durin...

Background Use of bio-based diesel is increasing in Europe. It is currently produced from oilseed crops, but can also be generated from lignocellulosic biomass such as straw. However, removing straw affects soil organic carbon (SOC), with potential consequences for the climate impact of the biofuel. This study assessed the climate impacts and energ...

Lipids are essential for any organism. They are hydrophobic compounds and include, for instance, acylglycerides, free fatty acids, sterols and isoprenoids. Their synthesis starts from acetyl-CoA, which is converted to lipids by a variety of complex biochemical reactions. Lipids consist of highly reduced molecules, and the redox factor providing ele...

Liquid biofuels have great potential to replace fossil transportation fuels. Bioethanol, the current major biofuel, is mainly produced using the yeast Saccharomyces cerevisiae. However, present biofuels are largely generated from first generation, i.e. food grade, raw materials. Second generation, lignocellulosic biomass represents an abundant and...

This study evaluated the effectiveness of solid-state fermentation with Arxula adeninivorans or Hypocrea jecorina to improve hygienic quality and digestibility of banana peels by mono-gastric animals. Green peels of cooking bananas (Musa AAA-group) were solid-state fermented in ziploc plastic bags for 14 d either non-inoculated or inoculated with A...

Rainbow trout (Oncorhynchus mykiss) were fed for 10 weeks on a diet containing either 30% fish meal (FM) or with 20, 40 and 60% replacement of fish meal protein with Saccharomyces cerevisiae (SC) or a mixture of Wickerhamomyces anomalus and S. cerevisiae (WA). Luminal contents and mucosal tissue from the distal intestine were collected and analysed...

BACKGROUND: Biodiesel is the main liquid biofuel in the EU and is currently mainly produced from vegetable oils. Alternative feedstocks are lignocellulosic materials, which provide several benefits compared with many existing feedstocks. This study examined a technical process and its mass and energy balances to gain a systems perspective of combi...

This study investigated lipid production from the hemicellulosic fraction of birch wood by the oleaginous yeast Lipomyces starkeyi. Birch wood chips were thermochemically pretreated by hot water extraction, and the liquid phase, containing 45.1 g/l xylose as the major sugar, 13.1 g/l acetic acid and 4.7 g/l furfural was used for cultivations of L....

Background It remains a challenge to perform de novo assembly using next-generation sequencing (NGS). Despite the availability of multiple sequencing technologies and tools (e.g., assemblers) it is still difficult to assemble new genomes at chromosome resolution (i.e., one sequence per chromosome). Obtaining high quality draft assemblies is extreme...

Ethanol and biogas are energy carriers that could contribute to a future energy system independent of fossil fuels. Straw is a favorable bioenergy substrate as it does not compete with food or feed production. As straw is very resistant to microbial degradation, it requires a pretreatment to insure efficient conversion to ethanol and/or methane. Th...

Dekkera bruxellensis is a non-conventional yeast normally considered a spoilage organism in wine (off flavours) and in the bioethanol industry. But it also has potential as production yeast. The species diverged from Saccharomyces cerevisiae 200 mya, before the whole genome duplication (WGD). However, it displays similar characteristics such as bei...

This study combined moist airtight storage of moist grain with pig feed fermentation. Starter cultures with the potential to facilitate both technologies were added to airtight stored moist crimped cereal grain, and the impact on storage microflora and the quality of feed fermentations generated from the grain was investigated. Four treatments were...

The study aimed at evaluating an effective sterilization–inoculation technique to facilitate silage research on the effect of forage microflora on fermentation variables. The sterilization effect of heating at 60°C for 3 h + 103°C for 15 h was tested on samples of grass, grass–clover, white clover and maize, pre-dried at 60°C to a dry-matter (DM) c...

http://link.springer.com/chapter/10.1007%2F978-3-642-55013-3_9 Biofuels, such as ethanol, biodiesel and biogas, have the potential to replace a large proportion of transportation fuels that presently are mainly produced from fossil raw materials. Bioethanol, which is the product of the fermentative energy metabolism of yeasts, is currently the majo...

Biofuels, such as ethanol, biodiesel and biogas, have the potential to replace a large proportion of transportation fuels that presently are mainly produced from fossil raw materials. Bioethanol, which is the product of the fermentative energy metabolism of yeasts, is currently the major biofuel on the global market. It is to a large extent generat...

The fatty acid (FA) profiles of two strains of the yeasts Wickerhamomyces anomalus and Blastobotrys (Arxula) adeninivorans at cultivation temperatures from 15°C-30°C were characterised. Beside of the common even numbered C16 and C18 FAs, substantial proportions of the uneven numbered C17:1 were found in both species. C18:3 (n-3) (alpha linolenic ac...

Adaptation of Dekkera bruxellensis to lignocellulose hydrolysate was investigated. Cells of D. bruxellensis were grown for 72 and 192 hours in batch and continuous culture, respectively (adapted cells). Cultivations in semisynthetic medium were run as controls (non-adapted cells). To test the adaptation, cells from these cultures were reinoculated...

Sawdust can be used to make pellets (biofuel) and particle boards and as a potential lignocellulose feedstock in bioethanol production. Microbial activity can affect sawdust quality; hence, we monitored the microbial population in birch- and spruce sawdust after 3 months' storage at various temperatures. Species composition was similar on both mate...

Lactobacillus vini was recently described as a contaminant in industrial ethanol fermentations and its cooccurrence with Dekkera bruxellensis was notified. We investigated the growth characteristics of L. vini in co-cultivation together with either Saccharomyces cerevisiae or D. bruxellensis. Lower cell numbers of both the yeasts and L. vini as wel...

The assimilation of nitrate, a nitrogenous compound, was previously described as an important factor favoring Dekkera bruxellensis in the competition with Saccharomyces cerevisiae for the industrial sugarcane substrate. In this substrate, nitrogen sources are limited and diverse, and a recent report showed that amino acids enable D. bruxellensis to...

Dekkera bruxellensis can outcompete Saccharomyces cerevisiae in environments with low sugar concentrations. It is usually regarded as a spoilage yeast but has lately been identified as an alternative ethanol production organism. In this study, global gene expression in the industrial isolate D. bruxellensis CBS 11270 under oxygen and glucose limita...

Expression levels of D. bruxellensis genes under oxygen and glucose limitation. Count designates the amount of reads mapped to the reference gene, RPKM is a measure of gene expression level expressed as number of reads per 1-K base pairs and million mapped reads. (DOCX)

A previous study showed that the use of nitrate by Dekkera bruxellensis might be an advantageous trait when ammonium is limited in sugarcane substrate for ethanol fermentation. The aim of the present work was to evaluate the influence of nitrate on the yeast physiology during cell growth in different carbon sources under oxygen limitation. If nitra...

Integrated storage and pre-treatment (ISP) combines biopreservation of moist material under airtight conditions and pre-treatment. Moist wheat straw was inoculated with the biocontrol yeast Wickerhamomyces anomalus, the xylan degrading yeast Scheffersomyces stipitis or a co-culture of both. The samples and non-inoculated controls were stored at 4 o...

The effect of glucose and oxygen limitation on the growth and fermentation performances of Dekkera bruxellensis was investigated in order to understand which factors favour its propagation in ethanol or wine plants. Although D. bruxellensis has been described as a facultative anaerobe, no growth was observed in mineral medium under complete anaerob...

The ascomycetous yeast Wickerhamomyces anomalus (formerly Pichia anomala and Hansenula anomala) exhibits antimicrobial activities and flavoring features that are responsible for its frequent association with food, beverage and feed products. However, limited information on the genetic background of this yeast and its multiple capabilities are curre...

Biopreservation of moist animal feed provides an alternative to conventional conservation methods and is often beside of saving energy and antimicrobial chemicals a way to improve feed quality. In regions with temperate climate drying of cereal grains can require approximately 60% of the total energy input during plant husbandry. In tropical region...

Eleven of 13 Enterobacteriaceae species tested grew in moist stored wheat, highlighting a potential risk of this energy-saving airtight storage method. When Hansenula anomala was coinoculated, all Enterobacteriaceae species were significantly inhibited after 2 months of storage, six of them to below the detection limit.

Testing the ability of the alternative ethanol production yeast Dekkera bruxellensis to produce ethanol from lignocellulose hydrolysate and comparing it to Saccharomyces cerevisiae. Industrial isolates of D. bruxellensis and S. cerevisiae were cultivated in small-scale batch fermentations of enzymatically hydrolysed steam exploded aspen sawdust. Di...

Bacterial diversity was studied using PCR-DGGE, cloning and sequencing. DNA was isolated from digesta samples from stomach, ileum and colon of 28 weaned piglets (Large WhiteMong Cai) fed dry control feed, naturally fermented liquid feed (FE) and a liquid diet with inclusion of rice distiller's residue feed. General bacterial diversity was described...

Scheffersomyces stipitis and the closely related yeast Candida shehatae assimilated the L-amino acids glutamate, aspartate and proline as both carbon and nitrogen sole sources. We also found this rarely investigated ability in ascomycetous species such as Candida glabrata, C. reukaufii, C. utilis, Debaryomyces hansenii, Kluyveromyces lactis, K. mar...

Scheffersomyces stipitis PJH was mutagenized by random integrative mutagenesis and the integrants were screened for lacking the ability to grow with glutamate as sole carbon source. One of the two isolated mutants was damaged in the COX5 gene, which encodes a subunit of the cytochrome c oxidase. BLAST searches in the genome of Sc. stipitis revealed...

Using standard laboratory equipment, thermochemically pretreated oat straw was enzymatically saccharified and fermented to ethanol, and after removal of ethanol the remaining material was subjected to biogas digestion. A detailed mass balance calculation shows that, for steam explosion pretreatment, this combined ethanol fermentation and biogas dig...

Cereal grain is a major component of food and feed in large parts of the world. The microbial flora on cereal grains may interfere with hygiene and storage stability, palatability and bioavailability of minerals and proteins may depend on the composition of the microbial population. Therefore, it is of primary interest to control the microbial spec...

This chapter will focus on the control of fungal growth in animal feed of plant origin, i.e. forage and cereal grain, and primarily on the use of biopreservation to improve feed hygiene. Microbes may interfere with the hygiene and storage stability of feed and different by-products utilised in the feed industry; reduce palatability of the feed; and...

The first International Pichia anomala Symposium provided a survey of past, recent and ongoing research on this yeast. The research community working with this yeast has focussed on several areas. Based on molecular data, a revision of the taxonomy is required: the name P. anomala is no longer applicable, as the genus Pichia is polyphyletic. The cu...

The influence of pH, temperature and carbon source (glucose and maltose) on growth rate and ethanol yield of Dekkera bruxellensis was investigated using a full-factorial design. Growth rate and ethanol yield were lower on maltose than on glucose. In controlled oxygen-limited batch cultivations, the ethanol yield of the different combinations varied...