Hydrolysis of citrus peel waste with recombinant rhamnosidase for bioenergy generation

Large amounts of Citrus peel (rich in poly-phenolic compounds) are generated as a by-product of the juice processing industry. Development of alternative, higher valued products utilizing peel waste from grapefruit, oranges, Valencia and other citrus fruit would benefit citrus juice processors by providing them with means to profitably process their peel waste and to avoid environmentally hazardous dumping. Citrus peel waste [CPW, comprised of peel, membranes and juice vesicles] contains a high level of polyphenols and has been used for the production of animal feed, single-cell protein, fibre, enzyme(s), immobilization support & bio-sorbent for heavy metal removal. Naringin (a major tri-hydroxy flavonoid glycoside) is available in large amounts in citrus peel, processed juice and can be extracted from citrus peel waste1. The extracted naringin is further hydrolysed by rhamnosidase to produce D-rhamnose for the production of ethanol and other fermentation products. We have produced a recombinant enzyme2 that has the ability to catalyse the cleavage of terminal rhamnoside groups from naringin to prunin and rhamnose. We have recovered important sugar “D-rhamnose” from the processed waste which would be utilized for ethanol production3. This presentation will summarize current efforts to develop an enzymatic treatment which would facilitate the economical processing of citrus waste for bioenergy generation.

Tailoring enzymes for biofuel production with reference to Australian biomass

Manufacture of biofuels from existing biomass may provide a sustainable alternative to the extensive utilization of fossil fuels. Biomass offers environmental advantage over fossil fuels as it is a renewable energy source with low sulphur and nitrogen content and is carbon neutral over its production and utilization. Ranges of biomass are reported worldwide to be suitable raw material for bioethanol production. These can be generally classified into three groups; sucrose based (sugar cane), starch based (corn, wheat and barley) and lignocellulosic (which is mostly comprised of lignin, cellulose and hemicelluloses in grasses, wood and straw) materials. However, the limited supply of two biomass groups (sucrose and starch) will not satisfy society’s growing energy demands; thus biofuel technology based on lignocelluloses is under intense investigation. The main bottleneck in lignocellulosic biomass conversion for biofuel production is the enzymatic depolymerisation of cell wall polysaccharides into fermentable sugars. Protein engineering has recently been used to improve the performance of lignocelluloses degrading enzymes, as well as proteins involved in biofuel synthesis pathways. We have produced a recombinant enzyme that has the ability to produce monomeric sugars from a complex substrate. This presentation will summarize current efforts to develop an enzymatic treatment which would facilitate the economical processing of biomass available in Australia for bioenergy generation.

Fermentative production of rhamnosidase from Staphylococcus xylosus MAK 2 in a bioreactor for bio-energy generation

Increasing concern about the environment, food and feed shortages and hike in the price of petroleum have stimulated interest in new ways of producing biofuels. The interest is rapidly increasing towards converting agricultural wastes to commercially valuable products. Biofuels made from waste biomass can offer immediate and sustained greenhouse gas advantages. In this direction, we are focusing on Citrus processing waste, a byproduct of juice manufacture, which contains high amount of flavonoids and polysaccharides. There is a considerable industrial interest in the enzymatic transformation of flavonoids to hydrolysis products; that offers a pathway to bio-energy generation. Rhamnosidase of bacterial origin are very few and thus are potentially subject for research.

Staphylococcus xylosus, Gram positive cocci, a nonpathogenic member of CNS family, isolated from soil was used to produce α-L-rhamnosidase. This new strain, so far unknown for the production of α-L-Rhamnosidase, was identified and characterized as Staphyloccocus sp. through biochemical tests and 16S DNA sequence analysis. Effect of various medium and process parameters like pH, temperature, aeration and agitation rates and inducer concentration were studied. Further, the enzyme activity was enhanced by adding the inducer and divalent metal ion to the optimised fermentation medium. We have recovered important sugars “rhamnose” and “galacturonic acid” from the processed waste which would be utilized for ethanol production. This presentation will summarize current efforts to develop an enzymatic treatment which would facilitate the economical processing of citrus waste for bioenergy generation.

Nanobiotechnology as a novel paradigm for enzyme immobilisation and stabilisation with potential applications in biodiesel production

Nanobiotechnology is emerging as a new frontier of biotechnology. The potential applications of nanobiotechnology in bioenergy and biosensors have encouraged researchers in recent years to investigate new novel nanoscaffolds to build robust nanobiocatalyt

Recent trends in nanomaterials immobilised enzymes for biofuel production

Application of nanomaterials as novel supporting materials for enzyme immobilisation has generated incredible interest in the biotechnology community. These robust nanostructured forms, such as nanoparticles, nanofibres, nanotubes, nanoporous, nanosheets, and nanocomposites, possess a high surface area to volume ratios that can cause a high enzyme loading and facilitate reaction kinetics, thus improving biocatalytic efficiency for industrial applications. In this article, we discuss research opportunities of nanoscale materials in enzyme biotechnology and highlight recent developments in biofuel production using advanced material supports for enzyme immobilisation and stabilisation. Synthesis and functionalisation of nanomaterial forms using different methods are highlighted. Various simple and effective strategies designed to result in a stable, as well as functional protein-nanomaterial conjugates are also discussed. Analytical techniques confirming enzyme loading on nanomaterials and assessing post-immobilisation changes are discussed. The current status of versatile nanomaterial support for biofuel production employing cellulases and lipases is described in details. This report concludes with a discussion on the likely outcome that nanomaterials will become an integral part of sustainable bioenergy production.

Microbial nanowires : an electrifying tale

Electromicrobiology has gained momentum in the last ten years with advances in microbial fuel cells and the discovery of microbial nanowires (MNWs). The list of MNWs producing microorganisms is growing and providing intriguing insights into the presence of such microorganisms in diverse environments and the potential roles MNWs can perform. This review discusses the MNWs produced by different microorganisms, including their structure, composition and role in electron transfer through MNWs. Two hypotheses, metallic-like conductivity and an electron hopping model, have been proposed for electron transfer and we present a current understanding of both these hypotheses. MNWs are not only poised to change the way we see microorganisms but may also impact the fields of bioenergy, biogeochemistry and bioremediation, hence their potential applications in these fields are highlighted here.