## 9 Insight on Homo- and Heterofermatative LAB
### Heterofermentative LAB  
Both facultative and obligate heterofermentative inoculums are involved in the silage-making process (_Lactobacillus, Oenococcus, Leucostoc, Weissella_). The most dominant LABs are _Lentilactobacillus buchneri, Limosilactobacillus reuteri, Lacticaseibacillus casei_[86]. Other LAB groups include _Levilactobacillus zymae, Apilactobacillus kunkeei, Levilactobacillus acidifarinae, Levilactobacillus hamurensis, Levilactobacillus brevis, Levilactobacillus spicheri, Frucilatobacillus fructivorans, Frucilatobacillus fructivorans, and Levilactobacillus hamme-sii_[87]. The obligate heterofermentative _L. buchneri_ is considered the best silage additive. These bacteria can increase aerobic stability during heterofermentation. It can synthesize antifungal components [88]. A recent report has also suggested _L. buchneri_ can strongly produce antimicrobial compounds (salicylic acid, 3-phenyl lactic acid, catechol, benzoic acid, hydrocinnamic acid, 4 hydroxybensoic acid) during grass silage fermentation [77]. These obligate heterofermentative bacteria (_L. buchneri_) can be used as silage additives to induce aerobic stability during silage fermentation. They can lead to a medium level of acetic acid increase and reduce contamination of yeast [89]. Recent reports have revealed heterofermentative additives _Lentilactobacillus diolivorans_ and _L. reuteri_ of silage [90]. The most potential role of _L. buchneri_ is that it can produce ferulic acid (esterase) in silage, leading to efficient fiber digestibility [91]. These heterofermentative bacteria can synthesize a sufficient amount of enzymes to produce suitable quantities of silages.  
Microbial additives have been exploited for enriching the fermentation process of silage. Heterofermentative LAB strains can produce lactic acid and carbon dioxide. They also produce very limited amounts of by-products such as acetic acid and ethanol [92]. Heterofermentative bacterial inoculants are essential to reduce the spoilage of silage [93]. These bacterial inoculants are advantageous in that they can improve the quality of fermentation for the silage [66]. Heterofermentative LABs at 55 to 60 d can significantly increase aerobic stability [4]. Heterofermentative LAB (_Lentilactobacillus diolivorans_, and _Lentilactobacillus hilgardii_) strains have potential antimicrobial activities. They can inactivate pathogens after enzyme exposure [94]. _L. hilgardii_ can synthesize a unique compound (phenyllactic and 4-hydroxyphenyllactic acid) that can fight against contaminants [95]. It has synergistic effects that increase aerobic stability and enhance prolonged fermentation of silages and other fermented foods [96] (S). It has been reported that _L. buchneri_ can convert lactate to 1,2-propanediol, which does not usually take place (\(\geq\) 21 d) during fermentation [97].  
A combination of numerous strains has been used as microbial inoculum. The production also varies using potential groups of _L. plantarum_, _P. acidilactici_, and _P. pentosaceus_[98]. The paring of inoculants for 14 days of fermentation can give a successful production of corn silage [99]. A multi-inoculum preparation for alfalfa _L. buchneri_ treated with _P. pentosaceus_ for one week has resulted in a greater pH decline than untreated silage. A combination of _L. buchneri_, _L. plantarum_, and _L. casei_ has been used for making barley silage on a lab scale [100]. The _P. pentosaceus_, _P. freudemeichii_, and _L. buchneri_ are the most commercial inoculants used for bermudagrass silage production. The combination of more inoculants can enhance the initial stage of the fermentation process [101].