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Biochemical Engineering Journal (v.44, #1)
Bioenergy: Sustainable fuels from biomass by yeast and fungal whole-cell biocatalysts by Hideki Fukuda; Akihiko Kondo; Sriappareddy Tamalampudi (pp. 2-12).
The dependency on depleting natural resources is a challenge for energy security that can be potentially answered by bioenergy. Bioenergy is derived from starchy and lignocellulosic biomass in the form of bioethanol or from vegetable oils in the form of biodiesel fuel. The acid and enzymatic methods have been developed for the hydrolysis of biomass and for transesterification of plant oils. However, acid hydrolysis results in the production of unnatural compounds which have adverse effects on yeast fermentation. Recent advancements in the yeast cell surface engineering developed strategies to genetically immobilize amylolytic, cellulolytic and xylanolytic enzymes on yeast cell surface for the production of fuel ethanol from biomass. Whereas in the case of biodiesel fuel production, alkali catalysis gives high levels of conversion in short reaction times. But complexity in the separation of produced biodiesel fuel from glycerol by-product led to intensive research on lipase enzyme and immobilized whole-cell biocatalysts. This system facilitates the easy separation of glycerol with the advantage of cost effectiveness. This review gives an insight in to the recent technological developments in the production of bioenergy, i.e., bioethanol and biodiesel fuel using surface engineered yeast and whole-cell biocatalysts.
Keywords: Bioenergy; Biomass; Cell surface engineering; Whole-cell biocatalyst; Bioethanol; Biodiesel fuel
Recent advances in solid-state fermentation by Reeta Rani Singhania; Anil Kumar Patel; Carlos R. Soccol; Ashok Pandey (pp. 13-18).
Solid-state fermentation (SSF) has built up credibility in recent years in biotech industries due to its potential applications in the production of biologically active secondary metabolites, apart from feed, fuel, food, industrial chemicals and pharmaceutical products and has emerged as an attractive alternative to submerged fermentation. Bioremediation, bioleaching, biopulping, biobeneficiation, etc. are the major applications of SSF in bioprocesses which have set another milestone. Utilization of agro-industrial residues as substrates in SSF processes provides an alternative avenue and value-addition to these otherwise under- or non-utilized residues. Innovation is the key to success and it is imperative to be up-to-date with the changing demands of the industries and meet their needs for better product and services. Better understanding of biochemical engineering aspects, particularly on mathematical modeling and design of bioreactors (fermenters) has made it possible to scale-up SSF processes and some designs have been developed for commercialization, making the technology economically feasible. In future, SSF technology would be well developed at par with SmF if rationalization and standardization continues in current trend. This review describes the state-of-art scenario in totality on SSF although the focus is on the most recent developments of last 5 years or so on SSF processes and products developments.
Keywords: Solid-state fermentation; Agro-industrial residues; Industrial products; Bioreactors; Modeling
Studies on potential applications of biomass for the separation of heavy metals from water and wastewater by Sisca O. Lesmana; Novie Febriana; Felycia E. Soetaredjo; Jaka Sunarso; Suryadi Ismadji (pp. 19-41).
Heavy metal pollution has become a more serious environmental problem in the last several decades as a result of its toxicity and insusceptibility to the environment. This paper attempts to present a brief summary of the role of biomass in heavy metal removal from aqueous solutions. Undoubtedly, the biosorption process is a potential technique for heavy metal decontamination. The current spectrum of effective adsorbents includes agricultural waste material, various algae, bacteria, fungi and other biomass. This paper also discusses the equilibria and kinetic aspects of biosorption. It was apparent from a literature survey that the Langmuir and Freundlich isotherms are by far the most widely used models for the biosorption equilibria representation, while pseudo-first and second order kinetic models have gained popularity among kinetic studies for their simplicity. Additional features on biosorption experiments utilizing a fixed bed column are also highlighted, as they offer useful information for biosorption process design.
Keywords: Biosorption; Heavy metals; Biosorbent
Recent developments in urea biosensors by Gunjan Dhawan; Gajjala Sumana; B.D. Malhotra (pp. 42-52).
This paper reviews recent developments in urea biosensors, as reported in the literature. The advantages and roles of various matrices, different strategies for biosensor construction, analytical performance and applications are discussed. The prospects of urea biosensors for medical applications are also discussed.
Keywords: Urea; Urease; Matrix; Biosensor
Recent advances in nanostructured biocatalysts by Jun Ge; Diannan Lu; Zhixia Liu; Zheng Liu (pp. 53-59).
Recent years have witnessed a renaissance in the field of chemically re-engineering of enzymes to obtain highly selective and efficient biocatalysts for catalyzing processes under various conditions. The incorporation of enzyme into nanostructured materials is particularly noteworthy from a structural perspective since there are unprecedented opportunities in such systems to establish suitable microenvironments for chosen enzymes. This review summarizes recent developments in the nanostructured biocatalyst with emphasis on those formed with polymers. Based on the synthetic procedures employed, the established methods are grouped into three major categories—“grafting onto”, “grafting from”, and “self-assembly”. The merits of the methods in enhancing enzyme stability at adverse conditions and their potential for large-scale preparation and the use of the nanostructured biocatalysts are discussed. The molecular fundamentals underlying each method are highlighted, and the use of molecular simulation as a tool for the design and application of nanostructured biocatalysts, although at a nascent stage, is presented. Finally, the problems encountered with nanostructured biocatalysts are discussed together with the future prospects of such systems.
Keywords: Nanostructured biocatalyst; Enzyme immobilization; Enzyme modification
A review of applications of cavitation in biochemical engineering/biotechnology by Parag R. Gogate; Abhijeet M. Kabadi (pp. 60-72).
Cavitation results in the generation of hot spots, highly reactive free radicals, and turbulence associated with liquid circulation currents, which can result in the intensification of various physical/chemical operations. The present work provides an overview of the applications of the cavitation phenomenon in the specific area of biochemical engineering/biotechnology, discussing the areas of application, the role of cavitation, the observed enhancement and its causes by highlighting some typical examples. The different methods of inducing cavitation and the dominance of one over the other, mostly with respect to energy requirements, in different areas of biotechnological application are discussed. The major applications discussed in the work include microbial cell disruption for the release or extraction of enzymes, microbial disinfection, wastewater treatment, crystallization, synthesis of biodiesel, emulsification, extraction of bio-components, freezing and gene transfer into cells or tissues. Some recommendations for optimal operating/geometric parameters have also been made. Overall, it appears that the combined efforts of physicists, chemists, biologists and chemical engineers are required to effectively use cavitational reactors for industrial applications.
Keywords: Cavitational reactors; Microbial cell disruption; Water disinfection; Biodiesel production; Biochemical engineering
Bacteria of the sulphur cycle: An overview of microbiology, biokinetics and their role in petroleum and mining industries by Kimberley Tang; Vikrama Baskaran; Mehdi Nemati (pp. 73-94).
Bacteria of the sulphur cycle, in particular sulphate reducing and sulphide oxidizing bacteria, are of immense importance from the industrial and environmental point of views. While biogenic production of H2S by sulphate reducing bacteria creates severe processing and environmental problems for the petroleum industry and agriculture sector, when used in a properly designed and controlled bioreactor sulphate reducing bacteria could play an instrumental role in the treatment of acid mine drainage, a major environmental challenge faced by the mining industry. Biooxidation of sulphide and intermediary sulphur compounds carried out by sulphide oxidizing bacteria are crucial in biotreatment of acid mine drainage and in the bioleaching of refractory minerals. Moreover, sulphide oxidizing bacteria are known as major players in the in situ removal of H2S from the onshore and offshore oil reservoirs and are used in the ex situ processes for the treatment of sour gas and sulphide laden waters. Owing to the numerous environmental and industrial applications, the bacteria of the sulphur cycle have been subject of numerous studies. The present article aims to provide an overview of the microbiology, biokinetics, current and potential applications of the bacteria of sulphur cycle and the reactions which are carried out by these versatile microorganisms. Special consideration is given to the role of these bacteria in the biotreatment of acid mine drainage, oil reservoir souring and the treatment of H2S-containing gaseous and liquid streams.
Keywords: Sulphur bacteria; Acid mine drainage; Oil reservoir souring; Biocorrosion; Sour gas; Microbial desulphurization; Biotreatment