Rapid and specific detection of Pentastiridius leporinus by recombinase polymerase amplification assay.

Pentastiridius leporinus (Hemiptera: Cixiidae) is the main vector of an emerging and fast spreading sugar beet disease, the syndrome 'basses richesses' (SBR), in different European countries. The disease is caused by the γ-3-proteobacterium 'Candidatus Arsenophonus phytopathogenicus' and the phytoplasma 'Candidatus Phytoplasma solani' which are exclusively transmitted by planthoppers and can lead to a significant loss of sugar content and yield. Monitoring of this insect vector is important for disease management. However, the morphological identification is time consuming and challenging as two additional cixiid species Reptalus quinquecostatus and Hyalesthes obsoletus with a very close morphology have been reported in sugar beet fields. Further, identification of females and nymphs of P. leporinus at species level based on taxonomic key is not possible. In this study, an isothermal nucleic acid amplification based on recombinase polymerase amplification (RPA) was developed to specifically detect P. leporinus. In addition, real-time RPA was developed to detect both adults (male and female) and nymph stages using pure or crude nucleic acid extracts. The sensitivity of the real-time RPA for detection of P. leporinus was comparable to real-time PCR, but a shorter time (< 7 min) was required. This is a first report for real-time RPA application for P. leporinus detection using crude nucleic acid templates which can be applied for fast and specific detection of this vector in the field.

Nighttime Applications of Germicidal UV Light to Suppress Cercospora Leaf Spot in Table Beet.

Cercospora leaf spot (CLS), caused by the hemibiotrophic fungus Cercospora beticola, is a destructive disease affecting table beet. Multiple applications of fungicides are needed to reduce epidemic progress to maintain foliar health and enable mechanized harvest. The sustainability of CLS control is threatened by the rapid development of fungicide resistance, the need to grow commercially acceptable yet CLS-susceptible cultivars, and the inability to manipulate agronomic conditions to mitigate disease risk. Nighttime applications of germicidal UV light (UV-C) have recently been used to suppress several plant diseases, notably those caused by ectoparasitic biotrophs such as powdery mildews. We evaluated the efficacy of nighttime applications of UV-C for suppression of CLS in table beet. In vitro lethality of UV-C to germinating conidia increased with increasing dose, with complete suppression at 1,000 J/m2. Greenhouse-grown table beet tolerated relatively high doses of UV-C without lethal effects despite some bronzing on the leaf blade. A UV-C dose >1,500 J/m2 resulted in phytotoxicity severities greater than 50%. UV-C exposure to ≤750 J/m2 resulted in negligible phytotoxicity. Older (6-week-old) greenhouse-grown plants were more susceptible to UV-C damage than younger (2- and 4-week-old) plants. Suppression of CLS by UV-C was greater when applied within 6 days of C. beticola inoculation than if delayed until 13 days after infection in greenhouse-grown plants. In field trials, there were significant linear relationships between UV-C dose and CLS control and phytotoxicity severity, and a significant negative linear relationship between phytotoxicity and CLS severity at the final assessment. Significant differences between UV-C doses on the severity of CLS and phytotoxicity indicated an efficacious dose near 800 J/m2. Collectively, these findings illustrate significant and substantial suppression by nighttime applications of UV-C for CLS control on table beet, with potential for incorporation in both conventional and organic table beet broadacre production systems.

Ecological characteristics of sugar beet plant and rhizosphere soil in response to high boron stress: A study of the remediation potential.

High boron (B) stress degrades the soil environment and reduces plant productivity. Sugar beet has a high B demand and potential for remediation of B-toxic soils. However, the mechanism regarding the response of sugar beet plants and rhizosphere soil microbiome to high B stress is not clear. In the potted soil experiment, we set different soil effective B environments (0.5, 5, 10, 30, 50, and 100 mg kg-1) to study the growth status of sugar beets under different B concentrations, as well as the characteristics of soil enzyme activity and microbial community changes. The results showed that sugar beet growth was optimal at 5 mg kg-1 of B. Exceeding this concentration the tolerance index decreased. The injury threshold EC20 was reached at an available B concentration of 35.8 mg kg-1. Under the treatment of 100 mg kg-1, the B accumulation of sugar beet reached 0.22 mg plant-1, and the tolerance index was still higher than 60%, which had not yet reached the lethal concentration of sugar beet. The abundance of Acidobacteriota, Chloroflexi and Patescibacteria increased, which was beneficial to the resistance of sugar beet to high B stress. In summary, under high B stress sugar beet had strong tolerance, enhanced capacity for B uptake and enrichment, and changes in soil microbial community structure. This study provides a theoretical basis for clarifying the mechanism of sugar beet resistance to high B stress and soil remediation.

In vitro fermentation characteristics of different types of fiber-rich ingredients by pig fecal inoculum.

BACKGROUND: Dietary fibers with varying physicochemical properties have different fermentation characteristics, which may differently impact host health. The present study aimed to determine the fermentation characteristics including gas production kinetics, short-chain fatty acids (SCFAs) production and microbial composition of different fibrous ingredients using in vitro fermentation by fecal microbiota. RESULTS: Sugar beet pule (SBP), wheat bran (WB), dried corn distillers grains with solubles (DDGS), rice bran (RB) and alfalfa meal (AM) were selected to fermentation in vitro for 36 h. The results showed that SBP had the greatest gas production. SBP had the highest in vitro dry matter fermentability (IVDMF) and production of acetate, propionate and total SCFAs, followed by WB, which were all greater than DDGS, AM and RB. The alpha-diversity was higher in the DDGS, AM and RB groups than in the WB and SBP groups. Differences in microbial community composition were observed among groups. The relative abundance of Treponema was highest in WB group. RB group showed lower Prevotella abundance than other groups but had higher Succinivibrio abundance. Interestingly, the Lactobacillus reached the highest abundances in the DDGS group. Correlation analysis indicated that the relative abundance of Treponema and Prevotella was positively associated with the gas production, IVDMF and SCFAs, whereas norank_f_Muribaculaceae, Rikenellaceae_RC9_gut_group, Lysinibacillus and Succinivibrio were the opposite. CONCLUSION: Collectively, WB and SBP were fermented rapidly by fecal microbiota compared to DDGS, AM and RB. Different fiber sources have different fiber compositions and fermentation properties that affect the microbial compositins and SCFAs production. © 2024 Society of Chemical Industry.

Hyperspectral Imaging in the UV Range Allows for Differentiation of Sugar Beet Diseases Based on Changes in Secondary Plant Metabolites.

Fungal infections trigger defense or signaling responses in plants, leading to various changes in plant metabolites. The changes in metabolites, for example chlorophyll or flavonoids, have long been detectable using time-consuming destructive analytical methods including high-performance liquid chromatography or photometric determination. Recent plant phenotyping studies have revealed that hyperspectral imaging (HSI) in the UV range can be used to link spectral changes with changes in plant metabolites. To compare established destructive analytical methods with new nondestructive hyperspectral measurements, the interaction between sugar beet leaves and the pathogens Cercospora beticola, which causes Cercospora leaf spot disease (CLS), and Uromyces betae, which causes sugar beet rust (BR), was investigated. With the help of destructive analyses, we showed that both diseases have different effects on chlorophylls, carotenoids, flavonoids, and several phenols. Nondestructive hyperspectral measurements in the UV range revealed different effects of CLS and BR on plant metabolites resulting in distinct reflectance patterns. Both diseases resulted in specific spectral changes that allowed differentiation between the two diseases. Machine learning algorithms enabled the differentiation between the symptom classes and recognition of the two sugar beet diseases. Feature importance analysis identified specific wavelengths important to the classification, highlighting the utility of the UV range. The study demonstrates that HSI in the UV range is a promising, nondestructive tool to investigate the influence of plant diseases on plant physiology and biochemistry.

Histopathological Investigation of Varietal Responses to Cercospora beticola Infection Process on Sugar Beet Leaves.

Cercospora leaf spot (CLS) is the most destructive foliar disease in sugar beet (Beta vulgaris). It is caused by Cercospora beticola Sacc., a fungal pathogen that produces toxins and enzymes which affect membrane permeability and cause cell death during infection. In spite of its importance, little is known about the initial stages of leaf infection by C. beticola. Therefore, we investigated the progression of C. beticola on leaf tissues of susceptible and resistant sugar beet varieties at 12-h intervals during the first 5 days after inoculation using confocal microscopy. Inoculated leaf samples were collected and stored in DAB (3,3'-diaminobenzidine) solution until processed. Samples were stained with Alexa Fluor-488-WGA dye to visualize fungal structures. Fungal biomass accumulation, reactive oxygen species (ROS) production, and the area under the disease progress curve were evaluated and compared. ROS production was not detected on any variety before 36 h postinoculation (hpi). C. beticola biomass accumulation, percentage leaf cell death, and disease severity were all significantly greater in the susceptible variety compared with the resistant variety (P < 0.05). Conidia penetrated directly through stomata between 48 to 60 hpi and produced appressoria on stomatal guard cells at 60 to 72 hpi in susceptible and resistant varieties, respectively. Penetration of hyphae inside the parenchymatous tissues varied in accordance with time postinoculation and varietal genotypes. Overall, this study provides a detailed account to date of events leading to CLS disease development in two contrasting varieties.

Seedborne Cercospora beticola Can Initiate Cercospora Leaf Spot from Sugar Beet (Beta vulgaris) Fruit Tissue.

Cercospora leaf spot (CLS) is a globally important disease of sugar beet (Beta vulgaris) caused by the fungus Cercospora beticola. Long-distance movement of C. beticola has been indirectly evidenced in recent population genetic studies, suggesting potential dispersal via seed. Commercial sugar beet "seed" consists of the reproductive fruit (true seed surrounded by maternal pericarp tissue) coated in artificial pellet material. In this study, we confirmed the presence of viable C. beticola in sugar beet fruit for 10 of 37 tested seed lots. All isolates harbored the G143A mutation associated with quinone outside inhibitor resistance, and 32 of 38 isolates had reduced demethylation inhibitor sensitivity (EC50 > 1 µg/ml). Planting of commercial sugar beet seed demonstrated the ability of seedborne inoculum to initiate CLS in sugar beet. C. beticola DNA was detected in DNA isolated from xylem sap, suggesting the vascular system is used to systemically colonize the host. We established nuclear ribosomal internal transcribed spacer region amplicon sequencing using the MinION platform to detect fungi in sugar beet fruit. Fungal sequences from 19 different genera were identified from 11 different sugar beet seed lots, but Fusarium, Alternaria, and Cercospora were consistently the three most dominant taxa, comprising an average of 93% relative read abundance over 11 seed lots. We also present evidence that C. beticola resides in the pericarp of sugar beet fruit rather than the true seed. The presence of seedborne inoculum should be considered when implementing integrated disease management strategies for CLS of sugar beet in the future.

Cell-Wall-Degrading Enzymes-Related Genes Originating from Rhizoctonia solani Increase Sugar Beet Root Damage in the Presence of Leuconostoc mesenteroides.

Sugar beet crown and root rot caused by Rhizoctonia solani is a major yield constraint. Root rot is highly increased when R. solani and Leuconostoc mesenteroides co-infect roots. We hypothesized that the absence of plant cell-wall-degrading enzymes in L. mesenteroides and their supply by R. solani during close contact, causes increased damage. In planta root inoculation with or without cell-wall-degrading enzymes showed greater rot when L. mesenteroides was combined with cellulase (22 mm rot), polygalacturonase (47 mm), and pectin lyase (57 mm) versus these enzymes (0-26 mm), R. solani (20 mm), and L. mesenteroides (13 mm) individually. Carbohydrate analysis revealed increased simpler carbohydrates (namely glucose + galactose, and fructose) in the infected roots versus mock control, possibly due to the degradation of complex cell wall carbohydrates. Expression of R. solani cellulase, polygalacturonase, and pectin lyase genes during root infection corroborated well with the enzyme data. Global mRNAseq analysis identified candidate genes and highly co-expressed gene modules in all three organisms that might be critical in host plant defense and pathogenesis. Targeting R. solani cell-wall-degrading enzymes in the future could be an effective strategy to mitigate root damage during its interaction with L. mesenteroides.

Nitrate and nitrite pathways and dynamic changes in bacterial communities during beet sugar processing.

BACKGROUND: Bacterial community successions were surveyed during the processing stages of sugar production using high-throughput sequencing methods. Furthermore, the correlation between bacterial community and nitrate/nitrite content in beet sugar processing were investigated. RESULTS: In an analysis of the V3-V4 region of the 16S rDNA gene, 254 122 effective sequences were obtained from samples, which included sugar beet, cossettes, diffusion juice, second-phase diffusion juice, light juice and thick juice. The results showed that dominant genera included Pantoea, Pseudomonas, Leuconostoc and Burkholderia. Moreover, significant changes in bacterial communities were observed in samples. Regarding the relevant nitrogen metabolic potential, this study revealed communities with the ability for nitrate and nitrite metabolism. Furthermore, a shaking experiment involving diffusion juice and second-phase diffusion juice was performed, and results showed that the nitrate level declined 73% and 98% in 36 h, respectively. These results suggested that the bacterial communities contribute to nitrate and nitrite transformation. CONCLUSION: This study illustrated that the bacterial communities and their specific effects on the formation of nitrate and nitrite during beet sugar processing. The results presented the basic concept involving the nitrate- and nitrite-forming pathways directly related to the mechanism of bacterial community growth. This study could facilitate an understanding of the correlation between nitrite content and microorganisms to guide beet sugar manufacturers regarding the control of nitrite and nitrate content. © 2021 Society of Chemical Industry.

Plant mitochondria and chloroplasts are targeted by the Rhizoctonia solani RsCRP1 effector.

The fungal species Rhizoctonia solani belongs to the Basidiomycota division and is a ubiquitous soil-borne pathogen. It is the main agent of the damping-off disease in seedlings and causes the root and crown rot disease in sugar beets. Plant pathogens deploy small secreted proteins, called effectors, to manipulate plant immunity in order to infect the host. Here, a gene (RsCRP1) encoded a putative effector cysteine-rich protein was cloned, expressed in Cercospora beticola and used for virulence assays. The RsCRP1 gene was highly induced upon the early-infection stage of sugar beet seedlings and disease was promoted. Confocal microscopy demonstrated localization to the chloroplasts and mitochondria upon transient expression of RsCRP1 in leaves of Nicotiana benthamiana. Further, this effector was unable to induce necrosis or to suppress hypersensitive response induced by the Avr4/Cf4 complex in N. benthamiana. Overall, these data indicate that RsCRP1 is a novel effector targeting distinct plant cell organelles in order to facilitate a successful infection at the early stages of the disease development.

Major latex protein-like encoding genes contribute to Rhizoctonia solani defense responses in sugar beet.

Sugar beets are attacked by several pathogens that cause root damages. Rhizoctonia (Greek for "root killer") is one of them. Rhizoctonia root rot has become an increasing problem for sugar beet production and to decrease yield losses agronomical measures are adopted. Here, two partially resistant and two susceptible sugar beet genotypes were used for transcriptome analysis to discover new defense genes to this fungal disease, information to be implemented in molecular resistance breeding. Among 217 transcripts with increased expression at 2 days post-infection (dpi), three resistance-like genes were found. These genes were not significantly elevated at 5 dpi, a time point when increased expression of three Bet v I/Major latex protein (MLP) homologous genes BvMLP1, BvMLP2 and BvML3 was observed in the partially resistant genotypes. Quantitative RT-PCR analysis on diseased sugar beet seedlings validated the activity of BvMLP1 and BvMLP3 observed in the transcriptome during challenge by R. solani. The three BvMLP genes were cloned and overexpressed in Arabidopsis thaliana to further dissect their individual contribution. Transgenic plants were also compared to T-DNA mutants of orthologous MLP genes. Plants overexpressing BvMLP1 and BvMLP3 showed significantly less infection whereas additive effects were seen on Atmlp1/Atmlp3 double mutants. The data suggest that BvMLP1 and BvMLP3 may contribute to the reduction of the Rhizoctonia root rot disease in sugar beet. Impact on the defense reaction from other differential expressed genes observed in the study is discussed.

Endophytic Microbiome Responses to Sulfur Availability in Beta vulgaris (L.).

Sulfur is an essential plant macronutrient, and its adequate supply allows an efficient root storage and sugar extractability in sugar beets (Beta vulgaris L.). In this study, we investigated the effect of changes in sulfur availability on the endophytic community structure of sugar beets. Plants were hydroponically grown in a complete nutrient solution (S-supplied), a nutrient solution without MgSO4 (S-deprived), and a nutrient solution without MgSO4 for six days and resupplied with 100 µM MgSO4 for 48 h (S-resupplied). The sulfur status was monitored by inductively coupled plasma ICP-OES, and combustion analysis together with the evaluation of microRNA395 as a biomarker for sulfate status. Metabarcoding of the bacterial 16S rRNA gene was carried out in order to determine leaf endophytic community structure. The Shannon diversity index significantly differed (p < 0.05) between sulfate-supplied and sulfate-deprived seedlings. Validation by Real-Time PCR showed a significant increase (p < 0.05) of Burkholderia spp. in sulfate-deprived plants as compared to sulfate-supplied ones. The study sheds new light on the effects of nutrient deficiency on the microbiome of sugar beet plants.

Valorisation of fungal hydrolysates of exhausted sugar beet pulp for lactic acid production.

BACKGROUND: Exhausted sugar beet pulp pellets (ESBPP) were used as raw material for lactic acid (LA) fermentation. The enzymatic hydrolysis of ESBPP was performed with the solid obtained after the fungal solid-state fermentation of ESBPP as a source of hydrolytic enzymes. Subsequently, a medium rich in glucose and arabinose was obtained, which was used to produce LA by fermentation. For LA production, two Lactobacillus strains were assayed and the effects of the supplementation of the hydrolysate with a nitrogen source and the mode of pH regulation of the fermentation were investigated. Moreover, a kinetic model for LA fermentation by Lactobacillus plantarum of ESBPP hydrolysates was developed. RESULTS: L. plantarum produced a LA concentration 34% higher than that produced by L. casei. The highest LA concentration (30 g L-1 ) was obtained with L. plantarum when the hydrolysate was supplemented with 5 g L-1 yeast extract and the pH was controlled with CaCO3 . The concentration of acetic acid differed depending on the concentration of CaCO3 added, producing its maximum value with 27 g L-1 CaCO3 . The proposed kinetic model was able to predict the evolution of substrates and products depending on the variation of the pH in the hydrolysate, according to the amount of CaCO3 added. CONCLUSIONS: ESBPP can be revalorised to produce LA. A pure LA stream or a mixture of LA and acetic acid, depending on the pH control method of the fermentation, can be produced. Thus, this control is of great interest depending on the destination of the effluent. © 2020 Society of Chemical Industry.

A longitudinal study on morpho-genetic diversity of pathogenic Rhizoctonia solani from sugar beet and dry beans of western Nebraska.

BACKGROUND: Root and stem rot caused by Rhizoctonia solani is a serious fungal disease of sugar beet and dry bean production in Nebraska. Rhizoctonia root rot and crown rot in sugar beet and dry bean have reduced the yield significantly and has also created problems in storage. The objective of this study was to analyze morpho-genetic diversity of 38 Rhizoctonia solani isolates from sugar beet and dry bean fields in western Nebraska collected over 10 years. Morphological features and ISSR-based DNA markers were used to study the morphogenetic diversity. RESULTS: Fungal colonies were morphologically diverse in shapes, aerial hyphae formation, colony, and sclerotia color. Marker analysis using 19 polymorphic ISSR markers showed polymorphic bands ranged from 15 to 28 with molecular weight of 100 bp to 3 kb. Polymorphic loci ranged from 43.26-92.88%. Nei genetic distance within the population ranged from 0.03-0.09 and Shannon diversity index varied from 0.24-0.28. AMOVA analysis based on ΦPT values showed 87% variation within and 13% among the population with statistical significance (p < 0.05). Majority of the isolates from sugar beet showed nearby association within the population. A significant number of isolates showed similarity with isolates of both the crops suggesting their broad pathogenicity. Isolates were grouped into three different clusters in UPGMA based cluster analysis using marker information. Interestingly, there was no geographical correlation among the isolates. Principal component analysis showed randomized distribution of isolates from the same geographical origin. Identities of the isolates were confirmed by both ITS-rDNA sequences and pathogenicity tests. CONCLUSION: Identification and categorization of the pathogen will be helpful in designing integrated disease management guidelines for sugar beet and dry beans of mid western America.

Full genome sequence of a new mitovirus from the phytopathogenic fungus Rhizoctonia solani.

A double-stranded RNA (dsRNA) segment was identified in Rhizoctonia solani anastomosis group (AG)-2-2IIIB, the primary causal agent of Rhizoctonia crown and root rot of sugar beet. The dsRNA segment represented the genome replication intermediate of a new mitovirus that was tentatively designated as "Rhizoctonia solani mitovirus 39" (RsMV-39). The complete sequence of the dsRNA was 2805 bp in length with 61.9% A+U content. Using either the fungal mitochondrial or universal genetic code, a protein of 840 amino acids containing an RNA-dependent RNA polymerase (RdRp) domain was predicted with a molecular mass of 94.46 kDa. BLASTp analysis revealed that the RdRp domain of RsMV-39 had 43.55% to 72.96% sequence identity to viruses in the genus Mitovirus, and was the most similar (72.96% identical) to that of Ceratobasidium mitovirus A (CbMV-A). Phylogenetic analysis based on RdRp domains clearly showed that RsMV-39 is a member of a distinct species in the genus Mitovirus of the family Mitoviridae. This is the first full genome sequence of a mycovirus associated with R. solani AG-2-2IIIB.

The RsRlpA Effector Is a Protease Inhibitor Promoting Rhizoctonia solani Virulence through Suppression of the Hypersensitive Response.

Rhizoctonia solani (Rs) is a soil-borne pathogen with a broad host range. This pathogen incites a wide range of disease symptoms. Knowledge regarding its infection process is fragmented, a typical feature for basidiomycetes. In this study, we aimed at identifying potential fungal effectors and their function. From a group of 11 predicted single gene effectors, a rare lipoprotein A (RsRlpA), from a strain attacking sugar beet was analyzed. The RsRlpA gene was highly induced upon early-stage infection of sugar beet seedlings, and heterologous expression in Cercospora beticola demonstrated involvement in virulence. It was also able to suppress the hypersensitive response (HR) induced by the Avr4/Cf4 complex in transgenic Nicotiana benthamiana plants and functioned as an active protease inhibitor able to suppress Reactive Oxygen Species (ROS) burst. This effector contains a double-psi beta-barrel (DPBB) fold domain, and a conserved serine at position 120 in the DPBB fold domain was found to be crucial for HR suppression. Overall, R. solani seems to be capable of inducing an initial biotrophic stage upon infection, suppressing basal immune responses, followed by a switch to necrotrophic growth. However, regulatory mechanisms between the different lifestyles are still unknown.

The effect of an additive containing three Lactobacillus species on the fermentation pattern and microbiological status of silage.

BACKGROUND: Appropriate combinations of lactic acid bacteria (LAB) strains should be selected to optimize the ensiling process, and the additives should be adjusted to the ensiled forage crops. The aim of this study was to determine the effect of inoculation with three Lactobacillus species on the chemical parameters and microbiological quality (beneficial and harmful microbiota) of grass silage. RESULTS: Three species: L. paracasei (LPa), L. brevis (LB) and L. plantarum (LPl), isolated from sugar beet silage and characterized based on 16S rDNA sequences and biochemical parameters, were analyzed in the study. Single strains and their combinations were used as silage inoculants. The basic chemical and microbiological (qPCR) parameters of silages were determined. Based on the results of agglomerative hierarchical clustering (AHC) and principal component analysis (PCA) it was determined that silages inoculated with single LAB strains and LPa + LB and commercial additive (0+) were the best quality ones, particularly with regard to microbiological parameters and they effectively lowered the pH value. A consortium of three Lactobacillus species had no influence on silage quality, whereas LPa + LB and LPl + LB combinations as well as a commercial additive exerted positive effects. Inoculation inhibited the growth of toxin-producing fungi. CONCLUSION: Only the appropriate LAB composition can improve the quality of the ensiled material (antagonistic relationship). Only the LPa + LB combination was able to improve the value of low dry silage; nevertheless, almost all combinations were able to reduced concentrations of toxin-producing fungi. © 2019 Society of Chemical Industry.

Cultivation and growth dynamics of endophytic fungi in a solid culture medium based on sugar beet pulp.

BACKGROUND: The production of mycelium from endophytic fungi is of interest for applications ranging from inoculants and biofertilizers for crop production to fermentations for enzyme and metabolite production. The purpose of this study was to test the capacity of a solid growth medium based on beet pulp for growing different strains of endophytes. RESULTS: The ergosterol content of inoculated medium was measured to estimate fungal growth. Several parameters related to the preparation of the growth medium, such as water content, calcium salts and incubation time, were evaluated. The greatest fungal biomass production was observed in a medium prepared with a 1:2 (beet pulp:water) ratio, containing calcium sulfate and carbonate. Strains belonging to different fungal species grew well in the growth medium finally selected, producing yields ranging from 50 to 500 g mycelium per kilogram of dry culture, after 22-27 days. Cultures containing up to 400 g beet pulp grew successfully, and could be scaled up. CONCLUSION: A solid culture medium based on beet pulp supported the growth of diverse taxa of fungal endophytes. Both the water and calcium salt content of the growth medium affected the efficiency of mycelium production. Considering these factors, beet pulp medium was an excellent endophyte cultivation medium because of the high yield of fungal biomass observed, together with its ease of handling and scaling-up production. © 2019 Society of Chemical Industry.

Bacterial growth dynamics and corresponding metabolite levels in the extraction area of an Austrian sugar beet factory using antimicrobial treatment.

BACKGROUND: During the manufacture of sucrose from sugar beet, different microorganisms originating from the plant material as well as from the soil enter the process. Due to the formation of polysaccharide-based slimes, these contaminants may induce several adverse effects such as filtration problems during juice purification. Certain microorganisms also metabolize sucrose, leading to product losses with financial consequences. To better understand and to prevent these negative effects, the aim of the study was to investigate the evolution of relevant bacterial groups, including their metabolites appearing during the extraction process. For this purpose, one production cycle was monitored to identify the major contamination steps and to clarify how they relate to the processing conditions. Traditionally, different antimicrobial agents such as formaldehyde, sulfur dioxide, hypochlorous acid, sodium hypochlorite, and chlorine dioxide have been added to inhibit microbial growth. In the present study, a rosin-based product derived from pine trees was applied as an alternative to those substances. RESULTS: Press water, raw juice, and mid-tower juice were identified as being highly contaminated with bacteria, and processing conditions such as time, temperature and pH level significantly influenced bacterial levels and the corresponding metabolites. Among the contaminants identified, lactic acid bacteria, and mesophilic and thermophilic aerobic bacteria played a dominant role, whereas lactic acid, acetic acid, butyric acid, and ethanol were identified as typical metabolites. CONCLUSION: Bacterial growth during production could be reduced by shock dosing of the rosin-based material in the extraction area. © 2020 Society of Chemical Industry.

Feasibility of exhausted sugar beet pulp as raw material for lactic acid production.

BACKGROUND: Exhausted sugar beet pulp pellets (ESBPP), a sugar industry by-product generated after sugar extraction in the sugar production process, have been used as a raw material for lactic acid (LA) production via hydrolysis and fermentation by Lactobacillus casei. To design a more cost-effective process, simultaneous saccharification and fermentation (SSF) of ESBPP is proposed in the present study. The effects of pH control, nutrient supplementation and solid addition in fed-batch SSF on lactic acid production were investigated. RESULTS: The highest LA concentration (26.88 g L-1 ) was reached in fed-batch SSF at a solid/liquid loading of 0.2 g mL-1 , with pH control (by adding 30 g L-1 CaCO3 to the medium) and nutrient supplementation (by adding 20 mL of MRS medium per 100 mL of buffer). Under these conditions, a maximum productivity of 0.63 g L-1 h-1 was achieved, which is 2.7 times higher than that attained in the control experiment (SSF inoculated at time 0 h). However, a slightly lower LA yield was obtained, revealing the need of an increasing dose of enzymes at high solid loading SSF. CONCLUSION: An efficient fed-batch SSF strategy with pH control and MRS supplementation is described in the present study, attaining higher LA productivity compared to separate hydrolysis and fermentation and SSF. © 2020 Society of Chemical Industry.