Table 2 Summary of biofuels and valued added chemicals production from insects and ruminants gut microbes
S. no | Source | Microbes | Substrate | Methane | VFA | Hydrogen | Ethanol | Others | Reference | |
|---|---|---|---|---|---|---|---|---|---|---|
Insects | ||||||||||
 1 | Termites (Termes hospes, Nasutitermes ephratae, Microcerotermes parvus, and Nasutitermes lujae) | Microbial consortium | Wheat straw | – | 2.2 to 5.8 g/L | – | – | – | [31] | |
 2 | Termite (Nasutitermes ephratae) | Microbial consortium | Wheat straw | – | 179.3 mCmol VFA/L | – | – | – | [167] | |
 3 | Termite (Odontotermes formosanus) | Co-cultures of Bacillus and Clostridium sp. | Glucose | – | – | 4.08 mmol/mL | – | – | [136] | |
Unautoclaved mango tree substrate | – | – | 1.605 mmol/mL | – | – | |||||
Cellulose | – | – | 1.42 mmol/mL | – | – | |||||
Humic acid | – | – | 0.706 mmol/mL | – | – | |||||
 4 | Termite (Globitermes sp.) | Enterobacter cloacae KBH3 | Glucose | – | – | 7.4 mmol/L/h | – | – | [139] | |
 5 | Termite (Nasutitermes lujae) | Clostridium termitidis strain CT1112 | Cellobiose | – | – | 4.6 mmol/L or 0.26 mmol/L/h | 3.7 mmol/L or 0.18 mmol/L/h | Acetate—5.9 mmol/L Lactate—2.0 mmol/L Formate—4.2 mmol/L CO2—5.6 mmol/L | [140] | |
Clostridium termitidis strain CT1112 | α-Cellulose | – | – | 7.7 mmol/L or 0.14 mmol/L/h | 3.1 mmol/L or 0.06 mmol/L/h | Acetate—7.2 mmol/L Lactate—0.5 mmol/L Formate—2.9 mmol/L CO2—6.9 mmol/L | ||||
 6 | Termite (Cubitermes speciosus) | Clostridium mayombei sp. | Glucose | – | – | 13.4 mmol/100 mmol of substrate | – | Acetate—251.5 mmol/100 mmol of substrate CO2—6.7 mmol/100 mmol of substrate | [171] | |
Xylose | – | – | – | – | Acetate—206.4 mmol/100 mmol of substrate | |||||
 7 | Termite (Pterotermes occidentis) | Acetonema longum gen | Glucose | – | – | 88.9 mmol/100 mmol of substrate | – | Acetate—17.3 mmol/100 mmol of substrate Propionate—10.2 mmol/100 mmol of substrate CO2—137.0 mmol/100 mmol of substrate | [142] | |
 8 | Superworm (Zophobas morio) | Midgut extracts | microcrystalline cellulosic substrates MCC 20 | – | – | – | – | Reducing sugar—2.480 mg/mL | [122] | |
Larvae | MCC 20 | – | – | – | – | Reducing sugar—0.399 mg/mL | ||||
 9 | Tipula abdominalis larvae | Cellulolytic bacterial isolate 27C64  + S. cerevisiae | Pre-treated pine | – | – | – | 29.8 g/L | – | [127] | |
 10 | Termite (Coptotermes formosanus) | Meyerozyma guilliermondii SSA-1543 T, Vanrija humicola SSA-1544, Starmera dryadoides SSA—1549 T, Acidisoma tundra SSA-1560, Dyella sp. SSA-1562 T and Burkholderia sp. SSA-1567 T Saccharomyces | Saw dust | – | – | – | 25.5 g/L | – | [20] | |
Meyerozyma guilliermondii SSA-1543 T | – | – | – | 13.9 g/L | – | |||||
Vanrija humicola SSA-1544 | – | – | – | 8.4 g/L | – | |||||
 11 | Termite (Cryptotermes brevis) | Bacillus sp. BMP01 | Wheat straw | – | – | – | – | Reducing sugar—439 mg/g Saccharification efficiency—51.95% | [61] | |
Ochrobactrum oryzae BMP03 strain |  | – | – | – | – | Reducing sugar—360 mg/g Saccharification efficiency- 42.60% | ||||
 12 | Termite gut (Reticulitermes chinensis) | Candidapseudorhagii sp. nov. strain SSA-1542 T | D-xylose | – | – | – | 14.7 g/L or 0.31 g/g | – | [129] | |
Hamamotoa lignophila sp. nov. strain SSA-1576 T | – | – | – | 10.1 g/L or 0.22 g/g | – | |||||
 13 | Beetle | Spathaspora passalidarum | Xylose | – | – | – | 0.41 g/g | – | [172] | |
Xylose + Cellobiose | – | – | – | 0.43 g/g | – | |||||
 14 | Beetle | S. stipites NRRL Y-7124 | Xylose | – | – | – | 0.39 g/g | – | [173] | |
S. passalidarum NN245 | – | – | – | 0.43 g/g | – | |||||
 15 | Scarab beetle | Promicromonospora pachnodae sp. | Glucose or xylose | – | – | – | 2.3–2.8 Mm | Lactate-2.9–3.0 mM Formate-0.5–0.7 mM | [32] | |
Ruminants | ||||||||||
 16 | Sheep Rumen | Cellulolytic bacterial culture | Wheat Straw | 196 mLN CH4/g VS | – | – | – | – | [151] | |
 17 | Bull rumen | Rumen fluid microbial consortium | Wheat Straw | 288.2 mL/g VS | – | 44.6 mL/g VS | – | Propionate—22.19 mmol Acetate—183.4 mmol | [152] | |
|  | Heifer rumen | 213 mL/g VS | – | – | – | – | ||||
 18 | Deer rumen | Rumen fluid microbial consortium | Glucose | - | – | 52 mol/100 mol of substrate | 17 mol/100 mol of substrate | Acetate—30 mol/100 mol of substrate Lactate—12 mol/100 mol of substrate | [134] | |
Fructose | – | – | 43 mol/100 mol of substrate | 20 mol/100 mol of substrate | Acetate—70 mol/100 mol of substrate Lactate—13 mol/100 mol of substrate | |||||
Ribose | – | – | 54 mol/100 mol of substrate | 3 mol/100 mol of substrate | Acetate—77 mol/100 mol of substrate Lactate—6 mol/100 mol of substrate | |||||
 19 | Cattle rumen | Clostridium xylanolyticum, Clostridium papyrosolvens, Clos—tridium beijerinckii, Ruminococcus sp., Ethanoligenens harbinense, and Desulfovibrio desulfuricans | Napier grass | – | – | Around 60 mL | – | Reducing sugar—around 0.20 mg/mL | [29] | |
 20 | Cattle rumen | C. puniceum Ru6 | Glucose | – | 2634 mg/L | 3379.2 mmol | Ethanol—126.6 mg/L | Butanol—42.4 mg/L | [131] | |
C. xylanolyticum Ru15 | Glucose | – | 1728 mg/L | 1970.6 mmol | 3418.1 mg/L | Butanol—47.4 mg/L | ||||
C. xylanolyticum Ru15 | Napier grass | – | 1405 mg/L | – | 1626 mg/L | – | ||||
C. puniceum Ru6 | Napier grass | – | 1667 mg/L | – | 72. 8 mg/L | – | ||||
 21 | Cattle | Rumen fluid | Rapeseed | 1901.7 mL of CH4 reactor−1 | Propionate—2.88 g/L Acetate—8.10 g/L | – | – | – | [115] | |
 22 | Cattle | Rumen fluid | Corn stover | – | 13,271 mg/L | – | – | – | [116] | |