Spirulina platensis (Arthrospira): Physiology, Cell Biology and Biotechnologym, edited by Avigad Vonshak

In the present period of information explosion and improved acces to published information internationally, there is need to consolidat e such information to help those who wish to surf through the literature for basi c and applied aspects . Spirulina has occupied a unique position in algal researc h and commercialisation for the past two decades . No other alga has been researche d so extensively in relation to its commercialisation, perhaps comparabl e only to Chlorella in the 1960s and ’70s. So much has been written, yet much moreneeds to be done. This book has contributions from leading researcher s on Spirulina, with eleven well presented chapters . The first four are dedicated to basi c aspects and contribute to identifying areaswhere thereshould be emphasi s on research . The rest of the book deals with application, problemsand future trends. Thetaxonomy of Spirulinahasalwaysbeen apoint of debate, with controversy concerning the use of the name Arthospi ra causing confusion in the naming of species . The topics of morphology, ultrastructur e and taxonomy aretreatedherewithclarity. Nodoubt DNAbased techniqueswil l be helpful in the future. For the timebeing, thenameSpirulina for Arthospi ra is likely to remai n in use. With commercial production being limited by photo-inhibition, photo-oxidation and reduction, the needtounderstan dphysiology ismoreurgent thanever. Aspect s of the photosyntheti c apparatus , the connectedelectrontranspor t systemsand their interactionsand the role of pigment s and light intensity are reviewed critically. The dynamics of phycobilisomes and the transfer of energy and heterogeneit y of photosynthetic systems make very interesting reading. The need for further work on C and N metabolism and regulation is well emphasised. Factors affecting growth rate, including environmental factors which ultimately affect the yield, are brought out clearly in the chapter on growth, physiology and biochemistr y. Details on certai n important enzymes are comprehens ive, but I would agree with theauthor’slament that nothingvery new hasemerged in the last ten yearson thebiochemistr y of Spirulina. Spirulina is not at present a model for genetic engineering studies, unlike some other well studied cyanobacteria . The lack of endogenou s plasmids and the presenc e of high content s of endonuclease s are cited asfactorshindering such studies. However, characterization of some Spirulina genes has been carried out and provides a step towards development of gene transfer systems. The areas connected to commercial aspect s are covered well in the last seven chapters. Thesteps in technology for outdoor Spirulina arewell knownanddocumente dhere,includingtheinfluenceof several environmental factors. Though theroleof light is considered at length, much less is said on nutrient and pH effects. A detailed cost-benefi t analysi s must be location specific, but the projection of investments needed for capital and running expenditureisgiven an overview. The convincing discussion on the need for cost reduction and other areas of improvement is an eyeopener. Tubular reactor s have been increasingl y promoted by workers in the west, particularl y stressing the improvedquality and yield. A start hasnow been made to developing these commerciall y, though production in closed reactor s has so far only reached the level of a few thousand liters. The challenges of circulating a huge culture volume in enclosed tubes and related problems are brought out well. The limitations on tubular reactor saremany, but thissystemwil l certainly haveitsnichein Spirulinaproduction in coming years. Several questions including feasibility and cost considerations need to be addressed . Flat-plate reactors which are used in laborator y studies on phototrophs haveonly recentl y been extended to Spirulina production. Though several benefit s are enumerated , bubble column platesseem at best only a distant possibility.