High-gravity worts

Ratkova J., Smogrovicova D., Domeny Z. and Bafrncova R. Very high gravity wort fermentation by immobilized yeast. Biotechnology letters 22 (14) (2000) 1173-1177. 

High gravity worts do not give such rapid clarification as worts of lower extract because the difference between the density of particles and the wort is less (Stokes Law). If no hop material is present, separation is poorer and the best result has been claimed for hop powder [26]. Additions of Irish Moss, polyvinylpyrrolidone, nylon 66 and particularly bentonite, have been stated to improve separation [26]. Anaerobic conditions are also said to increase the amount of material deposited, particularly by injecting carbon dioxide into the wort line when pumping into the whirlpool tank [26]. 

High-gravity and very-high-gravity wort fermentation... 

High-gravity worts usually require higher oxygen supply to ensure that the fermentation proceeds appropriately. Oxygen is essential for yeast growth and for unsaturated fatty acid (UFA) and sterol synthesis. Therefore, the supplementation with UFA... 

Huuskonen, A., Markkula, T., Vidgren, V, Lima, L., Mulder, L., Geurts, W., et al. (2010). Selection from industrial lager yeast strains of variants with improved fermentation performance in very-high-gravity worts. Applied and Environmental Microbiology, 76, 1563-1573. 

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