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Xylitol is a low calorie sweetener that can be produced through a bioconversion approach from lignocellulosic biomass that requires pre-treatment prior to the bioconversion of xylose to xylitol. Steam explosion (SE) is an industrially scalable pre-treatment (PT) process with the potential to liberate xylose monomers, however SE-PT has not been optimized for xylose release from multiple feedstock. The effect of pressure, substrate weight, phosphoric acid loading concentration and residence time on four feedstock [wheat straw (WS), corn stover (CS), Miscanthus (M), and willow (W)] for xylose release and minimal fermentation inhibitor production [furfural and 5-hydroxymethylfurfural (HMF)] was investigated using the Taguchi methodology for design of experiment (DoE) with variation at four levels (44). An L16 orthogonal array design was utilized and all factors indicated influence on xylose release and inhibitor formation and the resulting xylose rich hydrolysate assessed for bioconversion to xylitol. The L16 DoE gave hydrolysates containing 75–95% of xylose content in the original biomass, whilst retaining cellulose and lignin components in the fiber. The level of inhibitors were within boundary limits to enable microbial fermentation of the hydrolysates to xylitol. Fine tuning of the overall evaluation criteria (OEC) model imbibing 1.5 kg feedstock in 1.2% w/v orthophosphoric acid, 12 bar(g) and 6 min residence time resulted in 90% xylose recovery and production of >1,000 L of wheat straw hydrolysate for bioconversion to xylitol. The advantages and limitations of the Taguchi OEC model and further improvements to this process are discussed in a biorefining context.

Efficient utilization of lignocellulosic biomass requires pretreatment in order to liberate cellulose from lignin and disrupt its recalcitrant crystalline structure before effective enzymatic hydrolysis can take place. Three different pretreatment methods (pressure cooking with dilute alkali and dilute acid as well as alkaline extraction) to recover the xylooligosaccharides fraction from five different grass silage samples, whole crop rye silage and maize silage were compared. The predominant end products released were xylobiose, xylotetraose, xylopentaose and xylohexaose whereas the xylooligosaccharides release pattern differed with the substrate. Maximum values of xylooligosaccharides was found for grass silage 17.26 g/L, whole crop rye silage 3.06 g/L and for maize silage 5.77 g/L. Results reveal the production of high value by-products from agricultural biomass. Advantages of the green-biorefinery concept include a resulting liquid fraction after pretreatment with very low contents of inhibitors such ...

Agriculture significantly contributes to global greenhouse gas (GHG) emissions and there is a need to develop effective mitigation strategies. The efficacy of methods to reduce GHG fluxes from agricultural soils can be affected by a range of interacting management and environmental factors. Uniquely, we used the Taguchi experimental design methodology to rank the relative importance of six factors known to affect the emission of GHG from soil: nitrate (NO3-) addition, carbon quality (labile and non-labile C), soil temperature, water-filled pore space (WFPS) and extent of soil compaction. Grassland soil was incubated in jars where selected factors, considered at two or three amounts within the experimental range, were combined in an orthogonal array to determine the importance and interactions between factors with a L16 design, comprising 16 experimental units. Within this L16 design, 216 combinations of the full factorial experimental design were represented. Headspace nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) concentrations were measured and used to calculate fluxes. Results found for the relative influence of factors (WFPS and NO3- addition were the main factors affecting N2O fluxes, whilst glucose, NO3- and soil temperature were the main factors affecting CO2 and CH4 fluxes) were consistent with those already well documented. Interactions between factors were also studied and results showed that factors with little individual influence became more influential in combination. The proposed methodology offers new possibilities for GHG researchers to study interactions between influential factors and address the optimized sets of conditions to reduce GHG emissions in agro-ecosystems, while reducing the number of experimental units required compared with conventional experimental procedures that adjust one variable at a time.

The growing demand for sustainable animal production is compelling researchers to explore the potential approaches to reduce emissions of greenhouse gases from livestock that are mainly produced by enteric fermentation. Some potential solutions, for instance, the use of chemical inhibitors to reduce methanogenesis, are not feasible in routine use due to their toxicity to ruminants, inhibition of efficient rumen function or other transitory effects. Strategies, such as use of plant secondary metabolites and dietary manipulations have emerged to reduce the methane emission, but these still require extensive research before these can be recommended and deployed in the livestock industry sector. Furthermore, immunization vaccines for methanogens and phages are also under investigation for mitigation of enteric methanogenesis. The increasing knowledge of methanogenic diversity in rumen, DNA sequencing technologies and bioinformatics have paved the way for chemogenomic strategies by targeting methane producers. Chemogenomics will help in finding target enzymes and proteins, which will further assist in the screening of natural as well chemical inhibitors. The construction of a methanogenic gene catalogue through these approaches is an attainable objective. This will lead to understand the microbiome function, its relation with the host and feeds, and therefore, will form the basis of practically viable and eco-friendly methane mitigation approaches, while improving the ruminant productivity.

Laccase production by Coriolopsis caperata RCK2011 under solid state fermentation was optimized following Taguchi design of experiment. An orthogonal array layout of L18 (2(1) × 3(7)) was constructed using Qualitek-4 software with eight most influensive factors on laccase production. At individual level pH contributed higher influence, whereas, corn steep liquor (CSL) accounted for more than 50% of the severity index with biotin and KH2PO4 at the interactive level. The optimum conditions derived were; temperature 30°C, pH 5.0, wheat bran 5.0 g, inoculum size 0.5 ml (fungal cell mass = 0.015 g dry wt.), biotin 0.5% w/v, KH2PO4 0.013% w/v, CSL 0.1% v/v and 0.5 mM xylidine as an inducer. The validation experiments using optimized conditions confirmed an improvement in enzyme production by 58.01%. The laccase production to the level of 1623.55 Ugds(-1) indicates that the fungus C. caperata RCK2011 has the commercial potential for laccase.

The interest in xylitol has increased considerably in recent years, due to many commercial applications in different industrial sectors like food, dental related products, and pharmaceuticals. As industrial biotechnological routes to xylitol are costly they currently represents a small fraction of the marketshare. Therefore, over the past few decades much effort has been devoted to the development of cost-effective and environmentally-friendly biotechnological processes by evaluating cheaper lignocellulosic substrates. In this chapter, xylitol commercial processes, cost and market trends are discussed with a special focus on biorefining and biotechnological methods. Increasing commercial and scientific interest in xylitol has led to a strong demand for this product in the global market, of more than 125,000 tons per anum, with a value that is relatively high (4.5–5.5$/kg for bulk purchase by pharma/chewing gum companies and 12£ or 20$/kg in supermarkets) makes its an attractive proposition for commercialization.

Maximizing methane production while maintaining an appreciable level of process stability is a crucial challenge in the anaerobic digestion industry. In this study, the role of six parameters: the type of immobilizing supports, loading rate, inoculum levels, C:N ratio, trace nutrients concentrations and mixing rate, on methane production were investigated under thermophilic conditions (55 ± 1 °C) with synthetic substrate medium. The immobilizing supports were Silica gel, Sand, Molecular Sieve and Dowex Marathon beads. A Taguchi Design of Experiment (DOE) methodology was employed to determine the effects of different parameters using an L 16 orthogonal array. Overall, immobilizing supports influenced methane production substantially (contributing 61.3% of the observed variation in methane yield) followed by loading rate and inoculum which had comparable influence (17.9% and 17.7% respectively). Optimization improved methane production by 153% (from 183 to 463 ml CH 4 l −1 d −1 ).

A yeast-like fungus producing a large amount of extracellular polysaccharide was isolated from the biogas reactors at North Wyke Research, UK (latitude, 50°46′29″N; longitude, 3°55′23″W). This strain was identified as Aureobasidium pullulans based on nucleotide sequence of the D1/D2 domain of the large-subunit (LSU) rRNA gene. Extracellular polysaccharide or pullulan, produced from this new strain of A. pullulans in shake flasks and a stirred tank fermenter was investigated. A maximum polysaccharide concentration of 40.1 g l −1 , and productivity of 12.5 g l −1 per day was obtained in a batch culture from stirred tank fermenter. The optimal cultivation conditions for pullulan production for this strain in 250 ml shake flask containing 100 ml of sucrose medium were observed at 28 °C and with 200 rpm. The effect of different sugars and nitrogen sources on pullulan production was investigated. It was found that more pullulan was produced when the strain was grown in the medium supplemented with NaNO 3 than when it was cultivated in the medium supplemented with C5 and C6 sugars and other nitrogen sources.