Response of Wheat to a Multiple Species Microbial Inoculant Compared to Fertilizer Application

Microbial inoculants, including those formed from multiple species, may have dual functions as biostimulants and/or biocontrol agents, and claimed agricultural benefits are instrumental for regulatory categorisation. Biostimulants include commercial products containing substances or microorganisms that stimulate plant growth. Biostimulant microbes can be involved in a range of processes that affect N and P transformations in soil and thus influence nutrient availability, and N and P fertilizers can influence soil microbial diversity and function. A glasshouse experiment was conducted to investigate the effect of a multiple species microbial inoculant relative to a rock-based mineral fertilizer and a chemical fertilizer on wheat growth and yield, and on microbial diversity in the rhizosphere. The microbial inoculant was compared to the mineral fertilizer (equivalent to 5.6 kg N ha-1 and 5.6 kg P ha-1), and to the chemical fertilizer applied at three rates equivalent to: (i) 7.3 kg N ha-1 and 8.4 kg P ha-1 as recommended for on-farm use, (ii) 5.6 kg N ha-1 and 6.5 kg P ha-1 which matched the N in the mineral fertilizer, and (iii) 4.9 kg N ha-1 and 5.6 kg P ha-1 which matched P content in the mineral fertilizer. Despite an early reduction in plant growth, the microbial inoculant treatment increased shoot growth at maturity compared to the control. Similarly, grain yield was higher after application of the microbial inoculant when compared to control, and it was similar to that of plants receiving the fertilizer treatments. Using 16S rRNA sequencing, the microbial inoculant and fertilizer treatments were shown to influence the diversity of rhizosphere bacteria. The microbial inoculant increased the relative abundance of the phylum Actinobacteria. At tillering, the proportion of roots colonized by arbuscular mycorrhizal (AM) fungi increased with the microbial inoculant and mineral fertilizer treatments, but decreased with the chemical fertilizer treatments. At maturity, there were no treatment effects on the proportion of wheat roots colonized by AM fungi. Overall, the multiple species microbial inoculant had beneficial effects in terms of wheat yield relative to the commercial mineral and chemical fertilizers applied at the level recommended for on-farm use in south-western Australia

Microalgae and Phototrophic Purple Bacteria for Nutrient Recovery from Agri-Industrial Effluents; Influences on Plant Growth, Rhizosphere Bacteria, and Putative C & N Cycling Genes

Microalgae (MA) and purple phototrophic bacteria (PPB) have the ability to remove and recover nutrients from digestate (anaerobic digestion effluent) and pre-settled pig manure that can be utilized as a bio-fertilizer. The objective of this study was to compare the effect of biologically recovered nutrients from MA and PPB in relation to plant growth and soil biological processes involved in nitrogen & carbon cycling

Lactic acid production from food waste at an anaerobic digestion biorefinery: effect of digestate recirculation and sucrose supplementation

Low lactic acid (LA) yields from direct food waste (FW) fermentation restrict this production pathway. However, nitrogen and other nutrients within FW digestate, in combination with sucrose supplementation, may enhance LA production and improve feasibility of fermentation. Therefore, this work aimed to improve LA fermentation from FWs by supplementing nitrogen (0–400 mgN·L−1) as NH4Cl or digestate and dosing sucrose (0–150 g·L−1) as a low-cost carbohydrate. Overall, NH4Cl and digestate led to similar improvements in the rate of LA formation (0.03 ± 0.02 and 0.04 ± 0.02 h−1 for NH4Cl and digestate, respectively), but NH4Cl also improved the final concentration, though effects varied between treatments (5.2 ± 4.6 g·L−1). While digestate altered the community composition and increased diversity, sucrose minimised community diversion from LA, promoted Lactobacillus growth at all dosages, and enhanced the final LA concentration from 25 to 30 g·L−1 to 59–68 g·L−1, depending on nitrogen dosage and source. Overall, the results highlighted the value of digestate as a nutrient source and sucrose as both community controller and means to enhance the LA concentration in future LA biorefinery concepts

Developing a food waste biorefinery: Lactic acid extraction using anionic resin and impacts on downstream biogas production

Coupling lactic acid (LA) production with food waste (FW) anaerobic digestion (AD) can facilitate the next generation biorefinery to increase revenue and economic viability of FW AD. For this, LA should be effectively extracted from complex fermentation broths with minimal adverse effects on subsequent AD to maximise economic benefit. This study evaluated LA recovery by adsorption using a polymeric resin (BA765), not previously tested for LA, to explore adsorption capacity and kinetics. Furthermore, biochemical methane potential (BMP) tests were utilised to assess the effect of LA extraction on subsequent AD by measuring biogas production from the solid and liquid extraction residues. Optimal adsorption conditions yielded a maximum capacity of 0.21 gLA·g−1resin from pure solutions at pH 2–4, which was insensitive to temperature. However, real mixed fermentation broth impurities reduced LA uptake by 37%. BMP tests showed that the solid and liquid extraction residues had significant methane potential, with only a 21% reduction in overall methane yield compared to the raw fermentation broth prior to LA extraction. LA production outweighed the loss in methane energy in terms of relative value and indicated a FW biorefinery concept could be commercially attractive and technically feasible

Alterations to arbuscular mycorrhizal fungal community composition is driven by warming at specific elevations

Background Global warming can alter plant productivity, and community composition which has consequences for soil-plant associated microorganisms. Arbuscular mycorrhizal fungi (AMF) are distributed widely and form symbiotic relationships with more than 80% of vascular plants and play a key role in nutrient cycling processes at the ecosystem scale. Methods A simulated warming experiment at multiple elevations (3,000, 3,500, 3,800, and 4,170 m) was conducted utilizing an in-situ open-top chamber (OTC) for exploring the effect of global warming on AMF community structure in the Qinghai-Tibet Plateau (QTP). This region has been identified as one of the most sensitive areas to climatic changes. Soil DNA was extracted and sequenced using next the Mi-Seq platform for diversity profiling. Results AMF richness was higher under the simulated warming chamber, however this only occurred in the elevation of 3,500 m. Warming did not alter other AMF alpha diversity indices (e.g. Shannon, Ace, and Simpson evenness index). Glomus and Acaulospora were the dominate AMF genera as assessed through their relative abundance and occurrence in control and warming treatments at the different elevations. Conclusion Warming changed significantly AMF community. The effects of warming on AMF community structure varied depend on elevations. Moreover, the occurrences of AMF in different genera were also presented the different responses to warming in four elevations

Lactic acid from mixed food wastes at a commercial biogas facility: Effect of feedstock and process conditions

Anaerobic digestion facilities can become biorefineries to produce higher-value products together with biogas energy and nutrient-rich digestate. To inform future biorefinery concepts with lactic acid recovery, the current study monitored organic acids in a pre-fermentation stage at a commercial anaerobic digestion facility. The study assessed lactic acid production performance and the impact of mixed food waste feedstocks and process conditions. Feed rate and feedstock composition varied weekly with waste availability. Normal operating conditions of the pre-fermentation stage included warm ambient conditions (24–35 °C), low pH (3.45 ± 0.03), a short hydraulic retention time (1–3.5 days) and stable organic loading rate (12 ± 2 kgVS.m−3.day−1). These conditions favoured lactic acid, being dominant at an encouraging average concentration of 21.70 g L−1, notably without any process optimisation or control. Lactobacillus constituted the majority of the microbial community in the pre-fermentation stage (98.1 %–99.1 % relative abundance) with an unknown Lactobacillus species and L. reuteri being the major species present. Grain processing waste and milk paste were positive influencers of LA concentration. The monitoring results, together with a simple economic evaluation, indicated that lactic acid recovery from a commercial food waste anaerobic digestion facility had baseline feasibility. In addition, there would be significant opportunities to increase economic performance by targeted process control and optimisation

Microalgae and Phototrophic Purple Bacteria for Nutrient Recovery from Agri-Industrial Effluents; Influences on Plant Growth, Rhizosphere Bacteria, and Putative C & N Cycling Genes

Microalgae (MA) and purple phototrophic bacteria (PPB) have the ability to remove and recover nutrients from digestate (anaerobic digestion effluent) and pre-settled pig manure that can be utilized as a bio-fertilizer. The objective of this study was to compare the effect of biologically recovered nutrients from MA and PPB in relation to plant growth and soil biological processes involved in nitrogen & carbon cycling

Investigation of the Common Mycorrhizal Network Concept: Plant Growth Responses in Simulated Intercropping of a Legume and Grass under Water Stress

It is widely claimed that the common mycorrhizal network (CMN) plays a significant role in facilitated transfer of nutrients between plants. This experiment investigated the role of a common mycorrhizal network between a C3 legume and a C4 grass under nutrient and water-limited conditions

Microalgae and phototrophic purple bacteria for nutrient recovery from agri-industrial effluents: influences on plant growth, rhizosphere bacteria, and putative carbon- and nitrogen-cycling genes

Microalgae (MA) and purple phototrophic bacteria (PPB) have the ability to remove and recover nutrients from digestate (anaerobic digestion effluent) and pre-settled pig manure that can be Utilized as bio-fertilizer and organic fertilizer. The objective of this study was to compare the effectiveness of MA and PPB as organic fertilizers and soil conditioners in relation to plant growth and the soil biological processes involved in nitrogen (N) and carbon (C) cycling. To this end, a glasshouse experiment was conducted using MA and PPB as bio-fertilizers to grow a common pasture ryegrass (Lolium rigidum Gaudin) with two destructive harvests (45 and 60 days after emergence). To evaluate the rhizosphere bacterial community, we used barcoded PCR-amplified bacterial 16S rRNA genes for paired-end sequencing on the Illumina Mi-Seq. Additionally, we used phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) analysis for the detection of putative functional genes associated with N and soil-C cycling. There was a significant increase in plant growth when the soil was amended with PPB, which almost performed as well as the chemical fertilizers. Analysis of the rhizosphere bacteria after the second harvest revealed a greater abundance of Firmicutes than in the first harvest. Members of this phylum have been identified as a biostimulant for plant growth. In contrast, the MA released nutrients more slowly and had a profound effect on N cycling by modulating N mineralization and N retention pathways. Thus, MA could be developed as a slow-release fertilizer with better N retention, which could improve crop performance and soil function, despite nutrient losses from leaching, runoff, and atmospheric emissions. These data indicate that biologically recovered nutrients from waste resources can be effective as a fertilizer, resulting in enhanced C- and N-cycling capacities in the rhizosphere

Lactic acid from mixed food waste fermentation using an adapted inoculum: Influence of pH and temperature regulation on yield and product spectrum

Environmental conditions (pH and temperature) are expected to influence microbial community composition and product spectrum in mixed-culture food waste (FW) fermentation. However, some conditions may favour growth of multiple organisms that compete for common substrates or consume target metabolites. The inoculum plays an integral role in mixed-culture fermentation, but it is currently unknown how an adapted inoculum, known to selectively produce the target metabolite, would influence fermentation, and how environmental conditions could control fermentation outcomes. Therefore, this study assessed the effects of pH (uncontrolled vs. controlled pH 4.0–6.0) and temperature (35–60 ◦C) on lactic acid (LA) from synthetic mixed FW batch fermentation (80 gVS⋅L− 1) utilising an adapted fermentation inoculum known to produce significant LA (10% inoculum volume). Concentrations of LA and competing organic acids were measured. Uncontrolled pH encouraged Lactobacillus growth but resulted in a low LA yield due to inhibitory conditions. Controlled pH 6.0 improved LA production but introduced LA consumption and competitive butyrate production. Observed butyrate production was dependent on pH and temperature and correlated with the growth of Clostridium Sensu Stricto 12. At pH 6.0 and 50 ◦C, observable LA consumption was eliminated, and the LA yield was maximised at 0.55 gLA⋅gVS− 1 (39 gLA⋅L− 1) while Lactobacillus remained dominant. The adapted inoculum effectively promoted LA production, while pH and temperature regulation were effective control levers to target LA