Use of Penicillium bilaiae to improve phosphorus bioavailability of thermally treated sewage sludge:A potential novel type biofertiliser

This study explored the potential of different phosphorus (P)-rich sewage sludge biochars and ashes to be colonised and be used as a P sources for the phosphate-solubilising fungus, Penicilliurn bilaiae. P. bilaiae was inoculated on five different biochars and ashes supplemented with nutrient solution. Fungal colonisation, pH and water-extractable P (WEP) in the materials were determined after incubation.P. bilaiae colonised at similar rates on all materials tested, but colonisation was affected by glucose level, pH and total N content in the material. A pH decline, accompanied by an increase in WEP concentration, was observed in three materials. The amount of soluble P was significantly greater at the high glucose level and showed the largest relative increase in incineration ash (> 100-fold after 10 days). The results show a potential to use P-solubilising microorganisms to solubilise P from thermally converted sewage sludge, but the approach has to be further investigated regarding its effects in a soil/plant system

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Enhancing the phosphorus bioavailability of thermally converted sewage sludge by phosphate-solubilising fungi

Biochars and ashes from sewage sludge have a high phosphorus (P) content, but plant P availability is typically rather low. Phosphate-solubilising microorganisms (PSM) have been shown to have the ability to solubilise P from different compounds. The aim of this study was to explore the P-solubilisation potential of different PSM on various biochars and ashes, and the effect of the addition of different carbon (C) and nitrogen (N) sources on their P-solubilisation activity. The most promising combination of PSM, thermal residue and nutrients was then tested for its effect on plant growth and P uptake in a pot trial. Six PSM strains (four Penicillium bilaiae (Pb), one Penicillium aculeatum (Pa) and one Aspergillus niger (An)) were tested on two sewage sludge ashes and one biochar. Pb.4 and An showed the highest P-solubilisation rates on fluid-bed incineration (FB-I) ash. Pb.4 solubilised higher amounts of P when it was supplied with fructose in combination with NH4-N, while An performed equally well with fructose, maltose, mannose and xylose in combination with NH4-N. Increasing the concentration of the C source generally also increased the P solubilisation. However, when FB-I ash was inoculated with Pb.4 plus xylose/NH4-N and applied to spring wheat in a pot trial with gamma-irradiated soil, the inoculation did not significantly affect plant shoot biomass or P uptake. The results indicate that the amount and temporal availability of P solubilised by the fungal strain from the ash did not match plant requirements, suggesting that further work is required that focuses on further increasing solubilisation efficiency

Survival and phosphate solubilisation activity of desiccated formulations of Penicillium bilaiae and Aspergillus niger influenced by water activity

The impact of formulation and desiccation on the shelf life of phosphate (P)-solubilising microorganisms is often under-studied, particularly relating to their ability to recover P-solubilisation activity. Here, Penicilllium bilaiae and Aspergillus niger were formulated on vermiculite (V) alone, or with the addition of protectants (skimmed milk (V + SM) and trehalose (V + T)), and on sewage sludge ash with (A + N) and without nutrients (A), and dried in a convective air dryer. After drying, the spore viability of P. bilaiae was greater than that of A. niger. V formulations achieved the highest survival rates without being improved by the addition of protectants. P. bilaiae formulated on V was selected for desiccation in a fluidised bed dryer, in which several temperatures and final water activities (aw) were tested. The highest spore viability was achieved when the formulation was dried at 25 degrees C to a final aw > 0.3. During three months' storage, convective air dried formulations were stable for both strains, except in the presence of skimmed milk for P. bilaiae which saw a decrease in spore viability. In the fluidised bed-dried formulations, when aw > 0.3, the loss in viability was higher, especially when stored at 20 degrees C, than at aw < 0.1. P-solubilisation activity performed on ash was preserved in most of the formulations after desiccation and storage. Overall, a low drying temperature and high final aw positively affected P. bilaiae viability, however a trade-off between higher viability after desiccation and shelf life should be considered. Further research is needed to optimise viability over time and on more sustainable carriers

Fertilising effect of sewage sludge ash inoculated with the phosphate-solubilising fungus Penicillium bilaiae under semi-field conditions

Sewage sludge ashes provide interesting possibilities to recycle phosphorus (P) to soil, although the immediate plant availability is often low. The objective of this work was to increase the P-fertilising effect of sewage sludge ash through inoculation with the phosphate-solubilising fungus Penicillium bilaiae. In a soil incubation study, ash amendment enhanced the content of water-extractable P, but in contrast to previous in vitro experiments, inoculation with P. bilaiae did not further increase P availability, probably due to limited competitiveness of the fungus in soil. In a micro-plot field trial, a moderate P fertiliser effect of the ash was found without any additional effect of P. bilaiae ash inoculation on plant biomass and P-uptake. However, soil microbial functions determined by the MicroResp™ method were not negatively affected by the ash amendment. In conclusion, inoculation with P. bilaiae did not prove to be a suitable strategy to enhance P availability from sewage sludge ash. A better insight into the fungus’ ecology and colonisation ability in soil and rhizosphere as well as into its interactions with ash P is needed to further develop such alternative P-fertilising approaches

Succession of the wheat seed-associated microbiome as affected by soil fertility level and introduction of <i>Penicillium</i> and <i>Bacillus</i> inoculants in the field

During germination, the seed releases nutrient-rich exudates into the spermosphere, thereby fostering competition between resident microorganisms. However, insight into the composition and temporal dynamics of seed-associated bacterial communities under field conditions is currently lacking. This field study determined the temporal changes from 11 to 31 days after sowing in the composition of seed-associated bacterial communities of winter wheat as affected by long-term soil fertilization history, and by introduction of the plant growth-promoting microbial inoculants Penicillium bilaiae and Bacillus simplex. The temporal dynamics were the most important factor affecting the composition of the seed-associated communities. An increase in the relative abundance of genes involved in organic nitrogen metabolism (ureC and gdhA), and in ammonium oxidation (amoA), suggested increased mineralization of plant-derived nitrogen compounds over time. Dynamics of the phosphorus cycling genes ppt, ppx and cphy indicated inorganic phosphorus and polyphosphate cycling, as well as phytate hydrolysis by the seed-associated bacteria early after germination. Later, an increase in genes for utilization of organic phosphorus sources (phoD, phoX and phnK) indicated phosphorus limitation. The results indicate that community temporal dynamics are partly driven by changed availability of major nutrients, and reveal no functional consequences of the added inoculants during seed germination