Sreenivas Rao Ravella

New aspects and strategies for methane mitigation from ruminants

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.

Role of live microbial feed supplements with reference to anaerobic fungi in ruminant productivity: A review

Abstract To keep the concept of a safe food supply to the consumers, animal feed industries world over are showing an increasing interest in the direct-fed microbials (DFM) for improved animal performance in terms of growth or productivity. This becomes all the more essential in a situation, where a number of the residues of antibiotics and/or other growth stimulants reach in milk and meat with a number of associated potential risks for the consumers. Hence, in the absence of growth stimulants, a positive manipulation of the rumen microbial ecosystem to enhance the feedstuff utilization for improved production efficiency by ruminants has become of much interest to the researchers and entrepreneurs. A few genera of live microbes (i.e., bacteria, fungi and yeasts in different types of formulations from paste to powder) are infrequently used as DFM for the domestic ruminants. These DFM products are live microbial feed supplements containing naturally occurring microbes in the rumen. Among different DFM possibilities, anaerobic rumen fungi (ARF) based additives have been found to improve ruminant productivity consistently during feeding trials. Administration of ARF during the few trials conducted, led to the increased weight gain, milk production, and total tract digestibility of feed components in ruminants. Anaerobic fungi in the rumen display very strong cell-wall degrading cellulolytic and xylanolytic activities through rhizoid development, resulting in the physical disruption of feed structure paving the way for bacterial action. Significant improvements in the fiber digestibility were found to coincide with increases in ARF in the rumen indicating their role. Most of the researches based on DFM have indicated a positive response in nutrient digestion and methane reducing potential during in vivo and/or in vitro supplementation of ARF as DFM. Therefore, DFM especially ARF will gain popularity but it is necessary that all the strains are thoroughly studied for their beneficial properties to have a confirmed ‘generally regarded as safe’ status for ruminants.

Optimizing anaerobic digestion by selection of the immobilizing surface for enhanced methane production

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)).

Overview on Commercial Production of Xylitol, Economic Analysis and Market Trends

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

Production of xylooligosaccharides from renewable agricultural lignocellulose biomass

/kg for bulk purchase by pharma/chewing gum companies and 12£ or 20

Apiotrichum terrigenum sp. nov., a soil-associated yeast found in both the UK and mainland Europe

/kg in supermarkets) makes its an attractive proposition for commercialization.

Draft Genome Assemblies of Xylose-Utilizing Candida tropicalis and Candida boidinii with Potential Application in Biochemical and Biofuel Production

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 as furfural, hydroxymethylfurfural (HMF) and phenolic compounds.

Process Optimization of Steam Explosion Parameters on Multiple Lignocellulosic Biomass Using Taguchi Method—A Critical Appraisal

Five arthroconidium-producing yeast strains representing a novel Trichosporon-like species were independently isolated from the UK, Hungary and Norway. Two strains (Bio4T and Bio21) were isolated from biogas reactors used for processing grass silage, with a third strain (S8) was isolated from soil collected at the same UK site. Two additional strains were isolated in mainland Europe, one from soil in Norway (NCAIM Y.02175) and the other from sewage in Hungary (NCAIM Y.02176). Sequence analyses of the D1/D2 domains of the LSU rRNA gene and internal transcribed spacer (ITS) region indicated that the novel species belongs to the recently reinstated genus Apiotrichum and is most closely related to Apiotrichum scarabaeorum, a beetle-associated species first found in South Africa. Despite having similar physiological characteristics, the two species can be readily distinguished from one another by ITS sequencing. The species name Apiotrichum terrigenum sp. nov. is proposed to accommodate these strains, with Bio4T (=CBS 11373T=NCYC 3540T) designated as the type strain. The Mycobank deposit number is MB817431.

Biofuels Production from Renewable Feedstocks

ABSTRACT Non-albicans Candida species are growing in prominence in industrial biotechnology due to their ability to utilize hemicellulose. Here, we present the draft genome sequences of an inhibitor-tolerant Candida tropicalis strain (Y6604) and Candida boidinii NCAIM Y01308T.

Molecular Characterisation of Euryarchaeotal Community Within an Anaerobic Digester

Xylitol is a low calorie sweetener that can be produced through a bioconversion approach from lignocellulosic biomass that requires pretreatment prior to the bioconversion of xylose to xylitol. Steam explosion (SE) is an industrially scalable pretreatment (PT) process with the potential to liberate xylose monomers, however SE-PT has not been optimised 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 productions (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 utilised 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 fibre. 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 minutes residence time resulted in 90% xylose recovery and production of >1000 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