Flocculation in yeast means that the cells tend to stick together and form flocs of hundreds och thousands of cells. This can protect the cells from toxic substances or otherwise make them more durable in harsh conditions.
This is potentially very useful in industry, as it can facilitate fermentation of toxic substrates like acid hydrolysate and aid in separating the cells from the fermentation liquid. This is used in brewing beer. When the sugar in wort is depleted, the cells spontaneously flocculates and the beer can be decanted.
On a molecular level, the flocculation is casued by certain proteins in the cell wall. The proteins are called flocculins. They are hydrophobic and contain an active site that binds sugars. Mannitol binds the strongest and makes the flocculin proteins of one cell stick to mannoproteins in the cell wall or other cells.
The flocculins are produced by the FLO-genes. There are several different such genes known. FLO1, FLO5, FLO9 and FLO10 codes for flocculins. FLO8 is a transcription factor that regulates the expression of the other FLO genes. FLO11 also codes for a flocculin, but it is a bit different from the others. The Flo11 protein is extremely hydrophobic and makes the cells float to the surface. On the surface the yeast cells form a biofilm called a flor. This is used in fermenting certain Spanish wines.
You should look at research by Verstrepen, Mauricio, Westman and others.
Hi Sakhile
Some useful references on attachment 1
https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2010.04897.x/pdf
2
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwi6muedlarWAhXBCJoKHehlCLUQFghFMAQ&url=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC4552943%2F&usg=AFQjCNFqD3N_NmRdXtmKk_3Nf-RUrgjgeg
4
https://beta.nottingham.ac.uk/ncmh/documents/bger/volume-10/bger10-6.pdf
6
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&cad=rja&uact=8&ved=0ahUKEwi6muedlarWAhXBCJoKHehlCLUQFghpMAo&url=http%3A%2F%2Flink.springer.com%2F10.1007%2Fs00253-002-1200-8&usg=AFQjCNFTy586CoxIGM8bpyMfGeJy5ljYWg
7
https://www.ejbiotechnology.info/index.php/ejbiotechnology/article/view/v15n3-8/1449
11
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=14&cad=rja&uact=8&ved=0ahUKEwjh-se8l6rWAhWCbZoKHRZyDE84ChAWCDcwAw&url=https%3A%2F%2Flirias.kuleuven.be%2Fbitstream%2F123456789%2F283318%2F2%2FSVM-ApplMicrobiolBiotechnol.pdf&usg=AFQjCNEjCaafIoOYwegOTH7pdBzAmJLtWw
15
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=19&cad=rja&uact=8&ved=0ahUKEwjh-se8l6rWAhWCbZoKHRZyDE84ChAWCF8wCA&url=http%3A%2F%2Fscholar.sun.ac.za%2Fbitstream%2Fhandle%2F10019.1%2F1450%2Fgovender%2520p.pdf%3Fsequence%3D1&usg=AFQjCNETdmBb2tDQzWa4gf9XW40oqSQQ0w
17
https://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582012000300005
19
https://books.google.com/books?id=Z-RrbPSB2QQC&pg=PA158&lpg=PA158&dq=process+of+flocculation+in+yeast+strains&source=bl&ots=O9P25VeuOl&sig=LL4yyJZg1PomWXhevmSGbmG2jxs&hl=en&sa=X&ved=0ahUKEwjJxbjZmKrWAhVCLZoKHaCICoA4FBDoAQg3MAM
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