Novel refreshments with pleasant flavors were developed by fermentation of wort with basidiomycetes. Among 31 screened fungi, shiitake (Lentinula edodes) produced the most pleasant flavor. It was perceived as fruity, slightly sour, and plum-like. Flavor compounds were isolated by liquid-liquid extraction (LLE) and by headspace solid phase microextraction (HS-SPME). The key odor-active compounds were analyzed by a gas chromatography system equipped with a tandem mass spectrometry detector and an olfactory detection port (GC-MS/MS-O) and aroma extract dilution analysis (AEDA). For HS-SPME, a revised method of increasing the GC inlet split ratio was used. Most of the key odor-active compounds (e.g., 2-acetylpyrrole, β-damascenone, (E)-2-nonenal, and 2-phenylethanol) were detected with both extraction techniques. However, distinct differences between these two methods were observed.

Lignocellulosic biomass is the most abundant bioresource on earth containing polymers mainly consisting of d‐glucose, d‐xylose, l‐arabinose, and further sugars. In order to establish this alternative feedstock apart from applications in food, we engineered Pseudomonas putida KT2440 as microbial biocatalyst for the utilization of xylose and arabinose in addition to glucose as sole carbon sources. The d‐xylose‐metabolizing strain P. putida KT2440_xylAB and l‐arabinose‐metabolizing strain P. putida KT2440_araBAD were constructed by introducing respective operons from Escherichia coli. Surprisingly, we found out that both recombinant strains were able to grow on xylose as well as arabinose with high cell densities and growth rates comparable to glucose. In addition, the growth characteristics on various mixtures of glucose, xylose, and arabinose were investigated, which demonstrated the efficient co‐utilization of hexose and pentose sugars. Finally, the possibility of using lignocellulose hydrolysate as substrate for the two recombinant strains was verified. The recombinant P. putida KT2440 strains presented here as flexible microbial biocatalysts to convert lignocellulosic sugars will undoubtedly contribute to the economic feasibility of the production of valuable compounds derived from renewable feedstock.

Lignocellulose‐derived hydrolyzates typically display a high degree of variation depending on applied biomass source material as well as process conditions. Consequently, this typically results in variable composition such as different sugar concentrations as well as degree and the presence of inhibitors formed during hydrolysis. These key obstacles commonly limit its efficient use as a carbon source for biotechnological conversion. The gram‐negative soil bacterium Pseudomonas putida KT2440 is a promising candidate for a future lignocellulose‐based biotechnology process due to its robustness and versatile metabolism. Recently, P. putida KT2440_xylAB which was able to metabolize the hemicellulose (HC) sugars, xylose and arabinose, was developed and characterized. Building on this, the intent of the study was to evaluate different lignocellulose hydrolyzates as platform substrates for P. putida KT2440 as a model organism for a bio‐based economy. Firstly, hydrolyzates of different origins were evaluated as potential carbon sources by cultivation experiments and determination of cell growth and sugar consumption. Secondly, the content of major toxic substances in cellulose and HC hydrolyzates was determined and their inhibitory effect on bacterial growth was characterized. Thirdly, fed‐batch bioreactor cultivations with hydrolyzate as the carbon source were characterized and a diauxic‐like growth behavior with regard to different sugars was revealed. In this context, a feeding strategy to overcome the diauxic‐like growth behavior preventing accumulation of sugars is proposed and presented. Results obtained in this study represent a first step and proof‐of‐concept toward establishing lignocellulose hydrolyzates as platform substrates for a bio‐based economy.

The purpose of this study was to evaluate Cellvibrio japonicus as a potential host strain for one‐step bioconversion of hemicellulose polymers to value‐added products. C. japonicus could be cultivated on all main lignocellulose monosaccharides as well as xylan polymers as a sole carbon source. This is particularly interesting as most industrially relevant bacteria are neither able to depolymerize wood polymers nor metabolize most hemicellulose monosaccharides. As a result, lignocellulose raw materials typically have to be degraded employing additional processes while the complete conversion of all lignocellulose sugars remains a challenge. Exemplary for a value‐added product, a one‐step conversion of xylan polymers to mono‐rhamnolipid biosurfactants with C. japonicus after transformation with the plasmid pSynPro8oT carrying the genes rhlAB was demonstrated. As achieved product yields in this one‐step bioconversion process are comparably low, many challenges remain to be overcome for application on an industrial scale. Nonetheless, this study provides a first step in the search for establishing a future host strain for bioeconomy, which will ideally be used for bioconversion of lignocellulose polymers with as little exhaustive pretreatment as possible.

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