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It is necessary to find an appropriate strategy to simultaneously enhance the methane production and methane content in biogas from waste activated sludge (WAS) and grass co-digestion. In this study an efficient strategy, i.e., adjusting the initial pH 12 and C/N ratio 17/1, for simultaneous enhancement of methane production and methane content in biogas from WAS and perennial ryegrass co-digestion was reported. Experimental results indicated that the maximal methane production was 310 mL/gVS add at the optimum conditions after 30-d anaerobic digestion, which was, respectively, about 1.5- and 3.8-fold of the sole WAS and sole perennial ryegrass anaerobic digestion. Meanwhile, the methane content in biogas was about 74%, which was much higher than that of sole WAS (64%) or sole perennial ryegrass (54%) anaerobic digestion. [ABSTRACT FROM AUTHOR]

Abstract: Dielectric spectroscopy (DS) is routinely used in yeast and mammalian fermentations to quantitatively monitor viable biomass through the inherent capacitance of live cells; however, the use of DS to monitor the enzymatic break down of lignocellulosic biomass has not been reported. The aim of the current study was to examine the application of DS in monitoring the enzymatic saccharification of high sugar perennial ryegrass (HS-PRG) fibre and to relate the data to changes in chemical composition. DS was capable of both monitoring the on-line decrease in PRG fibre capacitance (C =580kHz) during enzymatic hydrolysis, together with the subsequent increase in conductivity (G =580kHz) resulting from the production of organic acids during microbial growth. Analysis of the fibre fractions revealed >50% of HS-PRG lignocellulose had undergone enzymatic hydrolysis. These data demonstrated the utility of DS biomass probes for on-line monitoring of simultaneous saccharification and fermentation (SSF). [Copyright &y& Elsevier]

Abstract: This study demonstrates use of recombinant yeast to simultaneously saccharify and ferment grass juice (GJ) to bioethanol. A modified Bacillus subtilis levanase gene (sacC) in which the native bacterial signal sequence was replaced with a yeast α-factor domain, was synthesised with yeast codon preferences and transformed into Saccharomyces cerevisiae (strain AH22) using the expression vector pMA91. AH22:psacC transformants secreted sacCp as an active, hyper-glycosylated (>180kDa) protein allowing them to utilise inulin (β[2-1] linked fructose) and levan (β[2-6] linkages) as growth substrates. The control (AH22:pMA91) strain, transformed with empty plasmid DNA was not able to utilise inulin or levan. When cultured on untreated GJ levels of growth and bioethanol production were significantly higher in experiments with AH22:psacC than with AH22:pMA91. Bioethanol yields from AH22:psacC grown on GJ (32.7[±4] mgmL−1) compared closely to those recently achieved () using enzymatically pre-hydrolysed GJ (36.8[±4] mgmL−1). [ABSTRACT FROM AUTHOR]

This study examined the feasibility of producing hydrogen by direct fermentation of fodder maize, chicory fructooligosaccharides and perennial ryegrass (Lolium perenne) in batch culture (pH 5.2–5.3, 35°C, heat-treated anaerobically digested sludge inoculum). Gas was produced from each substrate and contained up to 50–80% hydrogen during the peak periods of gas production with the remainder carbon dioxide. Hydrogen yields obtained were 62.4±6.1mL/g dry matter added for fodder maize, 218±28mL/g chicory fructooligosaccharides added, 75.6±8.8mL H2/g dry matter added for wilted perennial ryegrass and 21.8±8mL H2/g dry matter added for fresh perennial ryegrass. Butyrate, acetate and ethanol were the main soluble fermentation products. Hydrogen yields of 392–501m3/hectare of perennial ryegrass per year and 1060–1309m3/hectare of fodder maize per year can be obtained based on the UK annual yield per hectare of these crops. These results significantly extend the range of substrates that can be used for hydrogen production without pre-treatment. [Copyright &y& Elsevier]

• Broussonetia papyrifera ensiling with ryegrass in different ratios were studied. • Dynamic profiles of fermentation quality and bacterial community were evaluated. • Increasing mixing ratio of ryegrass resulted in high lactic acid production and low pH values. • Lactobacillus and Weissella dominated during the whole ensiling process. • Co-ensiling help to offer good forage resources for sustainable ruminant production. Broussonetia papyrifera (B. papyrifera) has been proposed to improve silage fermentation due to its high content of protein and abundant active plant extracts. Thus, dynamic profiles of fermentation quality and bacterial community of B. papyrifera mixing with perennial ryegrass in different ratios: 100:0, 90:10, 80:20, 70:30, 60:40, and 50:50 were examined during 60-d fermentation. Results showed that adding perennial ryegrass increased soluble carbohydrate content and lactic acid production in silage and decreased pH and population of epiphytic microorganisms. Adding ryegrass exerted a remarkable effect on the silage bacterial community with a dramatic decrease in the abundance of Enterobacter. Spearman's rank correlation showed that silage lactic acid concentration was positively correlated with Lactobacillus and Stenotrophomonas abundance, while ammonia nitrogen concentration was positively correlated with the abundance of Enterobacter. In conclusion, B. papyrifera ensiled with perennial ryegrass could improve B. papyrifera silage quality and provide high-quality forage resources for sustainable ruminant livestock production. [ABSTRACT FROM AUTHOR]