Nitrogen dynamics and biological processes in soil amended with microalgae grown in abattoir digestate to recover nutrients.

The use of microalgae for nutrient recovery from wastewater and subsequent conversion of the harvested biomass into fertilizers offers a sustainable approach towards creating a circular economy. Nonetheless, the process of drying the harvested microalgae represents an additional cost, and its impact on soil nutrient cycling compared to wet algal biomass is not thoroughly understood. To investigate this, a 56-day soil incubation experiment was conducted to compare the effects of wet and dried Scenedesmus sp. microalgae on soil chemistry, microbial biomass, CO2 respiration, and bacterial community diversity. The experiment also included control treatments with glucose, glucose + ammonium nitrate, and no fertilizer addition. The Illumina Mi-Seq platform was used to profile the bacterial community and in-silico analysis was performed to assess the functional genes involved in N and C cycling processes. The maximum CO2 respiration and microbial biomass carbon (MBC) concentration of dried microalgae treatment were 17% and 38% higher than those of paste microalgae treatment, respectively. NH4+ and NO3- released slowly and through decomposition of microalgae by soil microorganisms as compared to synthetic fertilizer control. The results indicate that heterotrophic nitrification may contribute to nitrate production for both microalgae amendments, as evidenced by low amoA gene abundance and a decrease in ammonium with an increase in nitrate concentration. Additionally, dissimilatory nitrate reduction to ammonium (DNRA) may be contributing to ammonium production in the wet microalgae amendment, as indicated by an increase in nrfA gene and ammonium concentration. This is a significant finding because DNRA leads to N retention in agricultural soils instead of N loss via nitrification and denitrification. Thus, further processing the microalgae through drying or dewetting may not be favorable for fertilizer production as the wet microalgae appeared to promote DNRA and N retention.

Development of a controlled release fertilizer by incorporating lauric acid into microalgal biomass: Dynamics on soil biological processes for efficient utilisation of waste resources.

Utilisation of microalgae to extract nutrients from the effluent of anaerobic digestion of food waste is an emerging technology. A by-product of this process is the microalgal biomass which has potential to be used as an organic bio-fertilizer. However, microalgal biomass are rapidly mineralized when applied to soil which may result in N loss. One solution is to emulsify microalgal biomass with lauric acid (LA) to delay the release of mineral N. This study aimed to investigate whether combining LA with microalgae to develop a new fertilizer product with a controlled release function of mineral N when applied to soil, and any potential impacts the bacterial community structure and activity. The treatments were applied to soil emulsified with LA and were combined with either microalgae or urea at rates of 0%, 12.5%, 25% and 50% LA, untreated microalgae or urea and unamended control were incubated at 25 °C and 40% water holding capacity for 28 days. Quantification of soil chemistry (NH4+-N, NO3--N, pH and EC), microbial biomass carbon, CO2 production and bacterial diversity were characterised at 0, 1, 3, 7, 14 and 28 days. The NH4+-N and NO3--N concentration decreased with increasing rate of LA combined microalgae indicating that both N mineralization and nitrification were impacted. As a function of time, NH4+-N concentration increased up to 7 days for the microalgae at lower rates of LA, and then slowly decreased for 14 and 28 days, with an inverse relationship with soil NO3-N. Aligning with soil chemistry, an observed decrease in the predicted nitrification genes amoA·amoB and relative abundance of ammonia oxidizing bacteria (Nitrosomonadaceae) and nitrifying bacteria (Nitrospiraceae) with an increasing rate of LA with microalgae provides further support for possible inhibition of nitrification. The MBC and CO2 production was higher in the soil amended with increasing rates of LA combined microalgae and there was an increase in the relative abundance of fast-growing heterotrophs. Treating microalgae by emulsification with LA has the potential to control the release of N by increasing immobilization over nitrification and therefore it might be possible to engineer microalgae to match plant nutrient growth requirements whilst recovering waste from waste resources.

Discovery of Two Chrysosporium Species with Keratinolytic Activity from Field Soil in Korea.

In an ongoing survey of Korean indigenous fungi, two fungal strains (KNU16-74 and KNU16-99) belonging to the genus Chrysosporium were isolated from field soil in Gyeongnam, Korea. Morphological characterization and phylogenetic analysis using sequence of the internal transcribed spacer regions were carried out to confirm its precise identification. These strains were identified as Chrysosporium indicum (KNU16-74) and Chrysosporium fluviale (KNU16-99). To examine the keratin degradation efficiency of these two fungal species, human hair strands were incubated with fungus culture. Results revealed that these two fungal species have the ability to degrade keratin substrate. This is the first report of these two species in Korea.

New Records of Aspergillus allahabadii and Penicillium sizovae from Crop Field Soil in Korea.

Two new records of Trichocomaceae, namely Aspergillus allahabadii and Penicillium sizovae, were isolated in 2016 during a survey of fungal diversity in different crop fields locations in Gyeongnam, Korea. These species were identified based on morphological characters and phylogenetic analysis using internal transcribed spacer region and ß-tubulin-encoding gene sequence data. A. allahabadii and P. sizovae have not yet been reported in Korea. Thus, this is the first report of these species in Korea, and their descriptions as well as details of their morphological characters are presented.

Three New Records of Ascomycetes Isolates from Field Soils in Korea.

Three new records of Ascomycota species (Chaetomium acropullum, Phialemonium globosum, Phialemonium atrogriseum) from field soils in Korea are presented in this study. These newly discovered fungal isolates were isolated from field soils from various places across Gyeongnam, Korea in 2016. All the isolates were identified and described based on morphological characteristics, and rDNA internal transcribed spacer and ß-tubulin gene sequence data. Morphological features of these fungal species were studied on different agar media: potato dextrose agar, oatmeal agar, malt extract agar, Czapek yeast extract agar, and yeast extract sucrose agar. Full description and illustrations of their morphological characters are provided. These fungal species have not officially been previously reported in Korea.