Simone Graeff-Hönninger

Effect of different C/N ratios on carotenoid and lipid production by Rhodotorula glutinis.

Due to the increasing demand for sustainable biofuels, microbial oils as feedstock for the transesterification into biodiesel have gained scientific and commercial interest. Also, microbial carotenoids have a considerable market potential as natural colorants. The carbon to nitrogen (C/N) ratio of the respective cultivation media is one of the most important parameters that influence the production of microbial lipids and carotenoids. Thus, in the present experiment, the influence of different C/N ratios, initial glucose loadings, and ammonium concentrations of the cultivation medium on microbial cell growth and lipid and carotenoid production by the oleaginous red yeast Rhodotorula glutinis has been assessed. As a general trend, both lipid and carotenoid production increased at high C/N ratios. It was shown that not only the final C/N ratio but also the respectively applied initial carbon and nitrogen contents influenced the observed parameters. The lipid yield was not affected by different ammonium contents, while the carotenoid production significantly decreased both at low and high levels of ammonium supply. A glucose-based increase from C/N 70 to 120 did not lead to an increased lipid production, while carotenoid synthesis was positively affected. Generally, it can be asserted that lipid and carotenoid synthesis are stimulated at higher C/N ratios.

Agroforestry in Europe: a review of the disappearance of traditional systems and development of modern agroforestry practices, with emphasis on experiences in Germany

Agroforestry is a new name for a rather old practice. From a historical point of view, various agroforestry systems existed in Europe, of which the wood pastures (Neolithicum), the Dehesas in Spain (~4,500 years old) and the Hauberg of the Siegerland (established in the Middle Age) are the most prominent. Other widespread systems in Europe were hedgerows, windbreaks and Streuobst (orchard intercropping). Due to mechanisation and intensification of agriculture, trees have been progressively removed from agricultural fields and traditional agroforestry systems slowly disappeared. Today, agroforestry systems are again increasing in interest as they offer the potential to solve important ecological and, especially, biodiversity problems, while at the same time enabling the production of food, wood products and fodder for cattle. Although agroforestry systems offer many advantages, many farmers are sceptical of these systems and are critical and risk-averse with regard to adopting new practices. However, in comparison to traditional systems, modern agroforestry systems can be adapted to current farming practices. By selecting suitable trees and appropriate tree management, high-quality timber can be produced without influencing agricultural crops excessively. In future, agroforestry systems will become increasingly important as they offer the prospect of producing woody perennials for bioenergy on the same land area as food and/or fodder plants, while enhancing overall biodiversity.

Soil-derived trace gas fluxes from different energy crops – results from a field experiment in Southwest Germany

Willow coppice, energy maize and Miscanthus were evaluated regarding their soil‐derived trace gas emission potential involving a nonfertilized and a crop‐adapted slow‐release nitrogen (N) fertilizer scheme. The N application rate was 80 kg N ha−1 yr−1 for the perennial crops and 240 kg N ha−1 yr−1 for the annual maize. A replicated field experiment was conducted with 1‐year measurements of soil fluxes of CH4, CO2 and N2O in weekly intervals using static chambers. The measurements revealed a clear seasonal trend in soil CO2 emissions, with highest emissions being found for the N‐fertilized Miscanthus plots (annual mean: 50 mg C m−² h−1). Significant differences between the cropping systems were found in soil N2O emissions due to their dependency on amount and timing of N fertilization. N‐fertilized maize plots had highest N2O emissions by far, which accumulated to 3.6 kg N2O ha−1 yr−1. The contribution of CH4 fluxes to the total soil greenhouse gas subsumption was very small compared with N2O and CO2. CH4 fluxes were mostly negative indicating that the investigated soils mainly acted as weak sinks for atmospheric CH4. To identify the system providing the best ratio of yield to soil N2O emissions, a subsumption relative to biomass yields was calculated. N‐fertilized maize caused the highest soil N2O emissions relative to dry matter yields. Moreover, unfertilized maize had higher relative soil N2O emissions than unfertilized Miscanthus and willow. These results favour perennial crops for bioenergy production, as they are able to provide high yields with low N2O emissions in the field.

The Rediscovery of Intercropping in China: A Traditional Cropping System for Future Chinese Agriculture – A Review

Intercropping has a 1000-year old history in Chinese agriculture and is still widespread in modern Chinese agriculture. Nowadays, agricultural systems in China are stigmatized to exhaust high levels of input factors like N fertilizer or irrigation water and to contribute severely to environmental problems like desertification, river eutrophication, soil degradation and greenhouse effect. In this context, monocropping systems have to be revised and may not be the best performing systems any more, considering sustainability, income security and nutritional diversity in rural areas. Therefore, intercropping systems offer alternatives for a more sustainable agriculture with reduced input and stabilized yield. Especially in the last decade this cropping system has been rediscovered by scientific research. Studies showed increased yield of maize and wheat intercropped with legumes: chickpea facilitates P uptake by associated wheat, maize intercropped with peanut improves iron nutrition and faba bean enhances N uptake when intercropped with maize. China’s intercropping area is the largest in the world. Nevertheless, there are only few international studies dealing with intercropping distribution, patterns and crops. Most studies deal with nutrient-use efficiency and availability. This study is a first approach to gain an overview of intercropping history, basic factors about interspecific facilitation and competition and distribution of Chinese intercropping systems. Finally, four intercropping regions can be distinguished and are explicitly described with their intercropping intensity, potential and conditions.

Biomass production potential from Populus short rotation systems in Romania

The aim of this study was to assess the potential of biomass production by short rotation poplar in Romania without constraining agricultural food production. Located in the eastern part of Europe, Romania provides substantial land resources suitable for bioenergy production. The process‐oriented biogeochemical model Landscape DNDC was used in conjunction with the forest‐growth model PSIM to simulate the yield of poplar grown in short‐rotation coppice at different sites in Romania. The model was validated on five sites with different climatic conditions in Central Europe. Using regional site conditions, with climatic parameters and organic carbon content in soil being the most important, the biomass production potential of poplar plantations was simulated for agricultural areas across Romania.

Chlorogenic acid, a metabolite identified by untargeted metabolome analysis in resistant tomatoes, inhibits the colonization by Alternaria alternata by inhibiting alternariol biosynthesis

Tomato fruits can be contaminated by saprophytic strains of Alternaria alternata which is the reason for the frequent occurrence of Alternaria toxins like alternariol, alternariol monomethylether or tenuazonic acid in these types of products. It was shown earlier that alternariol is a colonization factor for tomatoes. In the current analysis two different tomato genotypes were analysed by untargeted comprehensive two-dimensional gas chromatography mass spectrometry (GC×GC-MS). This analysis revealed clear differences in the metabolic profiles which were paralleled by differences in resistance towards Alternaria colonization. One of the genotypes was more resistant against A. alternata infection and contained high amounts of chlorogenic acid in contrast to the other genotype which was sensitive against infection. In in vitro analysis, chlorogenic acid reduced alternariol biosynthesis during the first days of growth of A. alternata. Expression analysis of the alternariol polyketide synthase gene, a key gene in the biosynthesis of alternariol, also revealed a temporal reduction in its expression in the first phases of growth. However by chromatographic analysis it could be demonstrated that chlorogenic acid was degraded over time. This degradation leads to a relief of inhibition resulting in an only temporal inhibition of alternariol biosynthesis. In vivo colonization experiments revealed that chlorogenic acid reduces colonization of tomatoes by A. alternata in a concentration dependent manner, which however is partly counteracted by the addition of alterariol.

Screening of industrial wastewaters as feedstock for the microbial production of oils for biodiesel production and high-quality pigments

The production of biodiesel has notably increased over the past decade. Currently, plant oil is the main feedstock for biodiesel production, but, due to concerns related to the competition with food production, alternative oil feedstocks have to be found. Oleaginous yeasts are known to produce high amounts of lipids, but no integrated process from microbial fermentation to final biodiesel production has reached commercial realization yet due to economic constraints. Therefore, growth and lipid production of red yeast Rhodotorula glutinis was tested on low-cost substrates, namely, wastewaters from potato, fruit juice, and lettuce processing. Additionally, the production of carotenoids as high-value by-products was examined. All evaluated wastewaters met the general criteria for microbial lipid production. However, no significant increase in lipid content was observed, probably due to lack of available carbon in wastewaters from fruit juice and lettuce processing, and excess of available nitrogen in potato processing wastewater, respectively. During growth on wastewaters from fruit juice and lettuce processing the carotenoid content increased significantly in the first 48 hours. The relations between carbon content, nitrogen content, and carotenoid production need to be further assessed. For economic viability, lipid and carotenoid production needs to be increased significantly. The screening of feedstocks should be extended to other wastewaters.

Characterization of different biomasses based on their sugar profile with focus on their utilization for microbial biodiesel production.

The investigation and characterization of different biomasses as potential feedstocks for microbial lipid production was the aim of the present work. Twenty-eight biomasses were analyzed for total sugar content (glucose and xylose) and C/N-ratio as two major criteria for a suitable lipid production by oleaginous microorganisms. Considering both parameters, 9 out of 28 biomasses seemed to be suitable feedstocks for microbial lipid production. To allow for a broad evaluation of the suitability of the potential feedstocks, the estimated sugar and potential energy yield per area were calculated and the production costs and energy demand of the feedstock production were considered.

A Modeling Approach to Simulate Effects of Intercropping and Interspecific Competition in Arable Crops

Interspecific competition between species influences their individual growth and performance. Neighborhood effects become especially important in intercropping systems, and modeling approaches could be a useful tool to simulate plant growth under different environmental conditions to help identify appropriate combinations of different crops while managing competition. This study gives an overview of different competition models and their underlying modeling approaches. To model intercropping in terms of neighbouring effects in the context of field boundary cultivation, a new model approach was developed and integrated into the DSSAT model. The results indicate the possibility of simulating general competition and beneficial effects due to different incoming solar radiation and soil temperature in a winter wheat/maize intercropping system. Considering more than the competition factors is important, that is, sunlight, due to changed solar radiation alone not explaining yield differences in all cases. For example, intercropped maize could compensate low radiation due to its high radiation use efficiency. Wheat benefited from the increased solar radiation, but even more from the increased soil temperature.

Economic assessment of microbial biodiesel production using heterotrophic yeasts

ABSTRACT The production of biodiesel using oleaginous microorganisms is investigated as promising alternative to produce a truly sustainable and renewable transportation fuel. While the feasibility of this approach has been shown on the laboratory scale, a commercial scale implementation is to date inhibited due to economic restraints. In order to evaluate the current cost situation and to develop suggestions to reduce production related costs, a simple cost analysis of the proposed microbial oil production process has been carried out. For closed fermentation in large-scale fermenters a break-even price of 2,350 US