“…A number of SSB designs exist for SSF, such as semi-continuous plug-flow [2], packed-bed [3][4][5][6][7], tray [8][9][10][11][12], trickle bed [13], multipurpose fixed-bed [14], rotating drum [9,15], horizontal drum [16], column-tray [17], novel deep-bed cubical [18], multi-layer packed-bed [19], column [20], fluidised-bed [21], hexahedral modular [22], SSF reactor (SSFR) [23], horizontal rotary drum [24], continuous counter-current [25], scrapped-drum [26], zymotis packed-bed [27], gas-solid spouted-bed [28], horizontal stirred tank [29], vertical cylindrical shaped (fed-batch SSF) [30] and cylindrical [31] bioreactors. Progress has been made in improving processes at the laboratory level, but research on bioreactor designs and process scale-ups that allow the usage of microorganisms needs further focus [32].…”